Hunting  for  Benchmarks

I quit!  Due to burnout and other factors, my benchmark hunting activity came to a stop on November 1, 2003.  One of the problems is that I work during almost all the daylight hours during the week, and my weekends are occupied by other interests.  Also I realized that I was wearing out my car (which already has almost 225,000 miles) looking for more and more remote benchmarks out in the suburbs.  All this, coupled with endlessly having to explain myself to relatives, onlookers, property owners and overzealous security guards, has led me to the decision to pull the plug on this hobby.  That's it.  I'm giving it up.


This is a benchmark.In the hotter months of 2003, I undertook the hobby of benchmark hunting.  After enjoying it for a while, I tired of it quickly, but I have left this page on line for the benefit of those who still have not heard of this activity, and those who still enjoy it.

Many people asked me what benchmark hunting is all about — usually while I was walking around in circles on a street corner, alternately looking at a data sheet and a GPS navigator, as I tried to find a metal marker buried under years of accumulated grass and dirt.  Benchmarks typically are small metal discs embedded in sidewalks or bridges.  Some qualify as triangulation stations.  They are used by surveyors as reference points; and their latitude, longitude, and altitude has been determined with great precision, in some cases several decades ago.  Many benchmark discs in the Dallas area are dated 1934, 1947, or 1986.  Apparently those were three good years for surveyors.  The newer style (1986 and later) consists of a metal rod, usually driven 20 feet or more into the ground, which is surrounded at the top by a protective cover and is flush with the ground.

The position of a benchmark is determined with great accuracy, as previously stated, however there are some which have had their coordinates "adjusted" to more precise figures, apparently after someone has made GPS measurements at the site.  Benchmarks were used as reference points long before anyone imagined a satellite navigation system like GPS.

This is a witness post.
The art and science of benchmark hunting is a mixture of GPS navigation, urban archaeology and digital photography.  Benchmarks are often covered with dirt and weeds and can be difficult to find.  It helps if the marker is accompanied by a "witness post", which is a warning sign usually posted about a foot from the mark, urging people to leave it alone.  (See illustration.)  Each benchmark also has a data sheet available, which gives a description of its location, but in many cases the descriptions are fifty years old, and some descriptions refer to buildings, airports or water towers which are long gone.  A hand-held GPS navigator is an essential tool for the serious benchmark hunter, since buildings and trees come and go but latitude and longitude are here to stay.

Hobbyists who locate a benchmark usually take a picture of it and its surroundings and upload the pictures to the Geocaching web site.  Close-up pictures are great for proving that you were there, but overview pictures help the next hunter find the mark. Quite often it is possible to find exactly the right location only to find that the marker has been destroyed, but this information is very helpful to others, and is posted so other people don't waste time looking for a marker that is no longer there.  In any event, when a benchmark is located, it is left alone, aside from brushing off the dirt to get a better picture.

Personally, I think finding water towers and church steeples is too easy, but I did not hesitate to use them to run up my score.  My final total of 172 benchmarks does not include 79 others for which I hunted, but was unable to locate, 20 places where I just visited the area and posted notes about the site, for one reason or another, and 12 marks which I have reported as destroyed.  (For example, I have been to five places where, in each case, there was supposed to have been a water tower, but it was obviously no longer there.  These I reported as "destroyed".)

Once I went digging in a public park with a spoon, looking for the MIDLOTHIAN marker, which was three inches underground.  That was probably my most difficult "find."

If you're interested, here is a list of the benchmarks I found.

If you're really interested, here is the complete list of all the benchmarks I found, tried to find, or didn't find, and the ones about which I posted other information.

If you look into the possibility of hunting for benchmarks in your area, you will find that some marks are listed in the government database but have been destroyed years ago by farm machinery, vandals, landscaping, or widening highways.  Some are exactly where they are supposed to be, but they're covered with dirt or weeds or tall grass, or they may have been painted over!  Others are in place but are accompanied by fire ants, stray dogs, poison ivy, heavy traffic or unfriendly neighbors.

  For more information about benchmarks, see "What is a benchmark?" at the   Geocaching web site.

 New:   Geocaching Turns Deadly.  Police say it looks like 64-year-old James Max Chamberlain fell off a small cliff at Eisenhauer Park in San Antonio.  Chamberlain went on the scavenger hunt Saturday morning [12/11/2004] using a hi-tech GPS system he had just bought.

Even if you know where something is, you can't necessarily get to it.  Be careful out there!

A word about photography near federal buildings:

In the current political climate, with all the talk of terror alerts and homeland security, there are a lot of security guards at federal buildings who are rather touchy about allowing photography.  Recently (9/3/2003) I ran into one such security guard who intercepted me just as I had located a benchmark at the Fort Worth Federal Building.  He told me that "photography of all federal facilities is prohibited."  This was rather discouraging, because I thought there was a chance that he could have been correct in his rash assertion, and perhaps this was a feature of the new Patriot Act of which I was unaware.  So the next day (9/4/2003) I went back to Fort Worth and talked to the security people at the Federal Building, including one very cooperative FPS officer who explained that photography of public buildings is not prohibited, nor could it ever be, as long as the Constitution is still in effect.  I was told instead that photography at any federal building is permissible as long as (1) you talk to the building manager first, and explain what you're doing, and (2) you don't take pictures of the guards, cameras, barriers, or any other components of the building security system.

Let's face it... if I were a spy or a terrorist, the security guards would never have known I was taking pictures.

Read this discussion among a bunch of other photographers who have experienced the same treatment, just for taking pictures!

See also The Photographer's Right - A Downloadable Flyer.  An explanation of your rights when stopped or confronted for photography.

Legal Rights of Photographers:  A clear explanation of what is legal to shoot and publish.

The Ultimate Legal Guide for Photographers.  Photographers are often confronted when they're taking photos.  The confrontation may take place between the photographer and private citizens or even with law enforcement.  You may be told to stop taking photos or you may be told that you have no rights to photograph the area or the people.  You do have rights as a photographer that you should know about.  Read this guide and keep it for future reference to protect yourself as a photographer.


I'm sure this looks like so much fun, you'll be tempted to take up this hobby yourself.  Before you do, let me offer a few words of caution:  When hunting for benchmarks, you are advised to observe the limits of private property, government property, restricted access areas, unsafe inner city neighborhoods, highway traffic lanes, and other hazardous areas.  This activity may also expose you to other risks, including (for example) inclement weather, exertion beyond your physical fitness level, adverse terrain, overzealous security guards (as explained above), insect bites, snake bites, dog bites, or exposure to poison ivy.  You assume the entire risk as to your use of the information on this page or any other page on this web site.  In no way shall anyone connected with be liable for any direct, indirect, punitive or consequential damages arising out of, or in any way connected with the use of this website, especially this page, or use of the information contained herein.  Read my disclaimer carefully.  Any actions you take based on whatever you saw, or think you saw, on this site are entirely your own responsibility.

 New!   I have put together a new page about the Camp Wisdom Triangulation Station,  located at 32° 40' 20.38" N., 96° 55' 50.06" W., at an altitude of 761 feet.

 Special Feature:   In Search of ARL5:  My field trip to the Arlington CORS station!  Be sure to see the latest pictures on the update page, Return to ARL5.

My search for Benchmark BN0594 at Longhorn Caverns, near Burnet, Texas.

The City of Cedar Hill, Texas, has its own benchmarks.  For example, Cedar Hill Benchmark #2009 (shown below) is located at 32° 36' 19.24328" N., 96° 56' 42.39458" W., at an altitude of 667.536 feet, and appears to be a Berntsen Model C1 marker.

 Photos of Cedar Hill Benchmark #2009:

Click to enlarge  Click to enlarge  Click to enlarge

When I took these pictures, Cedar Hill benchmark 2009 was in the middle of nowhere, just off a lonely road near some railroad tracks.  Right after these pictures were taken, a new neighborhood sprang up across the street!

Benchmark hunting is a spin-off of a hobby called Geocaching, in which people use GPS navigators to find a cache of goodies at some spot and sign the guestbook.  (Here is a brief explanation.)  This is obviously a great way to sell GPS navigation gear; however, Geocaching is potentially a way to get into a lot of trouble.  In most cases, the "hidden treasure" is on private property, or in areas which are off limits to the public, or in places where law-abiding people do not ordinarily go.  In any event, if you remove anything from someone else's cache, like GeoCoins for example (see below), it is suspicious behavior at best, and technically it is petty theft.  And you're at the mercy of everyone else who has visited that site, since anyone could stash illegal drugs or explosives or anything else in a GeoCache, and if you're caught with it in your hands, it's yours!  All I'm saying is that if you undertake this hobby, be prepared to spend the day explaining yourself to "badge happy" police officers, many of whom are a little too eager to take a bite out of crime.*

Click to enlarge  Signing the log book at a Geocache.  It was only about 100° that day.

Click to enlarge  Travis says, "You pick the strangest hobbies."  He's right.

Click to enlarge  Some Geocaches contain GeoCoins or Travel Bugs.

Various styles of Geocaching coins exist, [1]  [2]  [3]  [4]  [5]  or you could design your own!  Several companies make custom tokens and medallions.  [1]  [2] 

Geocaching:  A GPS Receiver is a Radio Too!  There's an Amateur Radio angle to this rapidly growing activity.

Related hobby:  The Degree Confluence Project:  The goal of the project is to visit each of the latitude and longitude integer degree intersections in the world, and to take pictures at each location.  So, for example, you might take your new hand-held GPS navigator out into the boonies and try to find exactly 30°N., 94°W.  (This spot is in a swamp southeast of Beaumont, and has only recently been photographed.  Maybe that's because there are probably at least three spiders per square foot in an area like that, not to mention the snakes.)  What fun!

Benchmark Hunting Terminology  explained at Benchmark Hunting  dot com.  A very professional-looking web site dedicated to this hobby.

Other benchmark hunting enthusiasts:  [1]  [2]  [3]

Photos of Survey markers and Witness Posts.

Make your own benchmarks.  The markers aren't very expensive.

Geodetic mark recovery  Maintenance and preservation of these marks is of utmost importance to users of the net and to NGSD [the National Geodetic Survey Division], recognizing that many valuable geodetic marks are destroyed by construction, new roads, erosion, or for other causes.

Back to the top of the page

Other material related to geography, latitude/longitude, GPS applications, etc.:

Find latitude and longitude of any spot on a map.
Convert latitude and longitude to bearing and distance.
TopoGrafix - Power Tools for your GPS!
Samuel J. Wormley's Waypoints:  Numerous interesting links
National Geodetic Survey
NGS Datasheet Retrieval Page for benchmark data sheets.
Place names database with numerous links.
GPS Web Tools : Latitude-Longitude of US Cities.
The Australian National Public Toilet Map.
Computing Azimuth and Elevation Angles with Javascript, for proper alignment of a satellite dish.

The Difference Between GPS and GIS.  Most people are familiar with the global positioning system (GPS).  After all, it is a technology that has become increasingly prevalent in day-to-day life, from navigation systems in cars to tracking the movement of wildlife in research programs.  The geographic information system (GIS) is less well-known, but without GIS, GPS could not possibly be used to its full potential.  GPS is a satellite-based navigation system, and GIS is a software program designed to store and manipulate the data that GPS accumulates.

Russian navigating devices on sale.  Navigating devices using Russian [Glonass] satellites will appear in the shops this year as the first alternative to the widely used GPS network of the United States, officials said overnight.

GPS helps cities catch goof-offs.  GPS tracking devices installed on government-issue vehicles are helping communities around the country reduce waste and abuse, in part by catching employees shopping, working out at the gym or otherwise loafing while on the clock.  The use of GPS has led to firings, stoking complaints from employees and unions that the devices are intrusive, Big Brother technology.  But city officials say that monitoring employees' movements has deterred abuses, saving the taxpayers money in gasoline and lost productivity.

A homemade receiver for GPS and GLONASS satellites by Matjaz Vidmar, S53MV.  This ham operator in Slovenia (?) went to a lot of trouble to build this equipment, and to prepare the documentation.  He has also undertaken many other experiments with UHF equipment.

GPS jamming incident in San Diego harbor in January 2007.  The U.S. Navy was conducting a scheduled communications jamming training exercise in the Port of San Diego.  Two Navy ships participated in the exercise for approximately two hours. … [Along with numerous other services, GPS was jammed] — unintentionally of course — and the jamming continued for approximately two hours.

Why 70 Miles Per Hour Is the New 55:  Left to their own devices, American drivers confronted with an open stretch of interstate highway tend to drive at about 70 miles per hour — whatever the legal speed limit happens to be.  That's the finding of an analysis of speed data gathered by TomTom Inc., a marketer of GPS navigation devices.

The Editor asks...
And how did they find out?  Is TomTom harvesting data from units in the field?

Why your trusty GPS sometimes fails you:  GPS navigation systems aren't perfect.  Most of them are pretty good, but blind acceptance of their advice can become a traveler's nightmare.

Should Homeland Security Control the GPS Network?  Americans have become accustomed to the presence of Global Positioning System (or GPS) technology embedded in everything from the GPS on their dash to their cell phones and iPads.  In fact, GPS is nearly taken for granted for everything from locating a restaurant to navigating a fishing boat through the fog.  But now it appears that GPS, which was developed primarily for its military applications, is rather overtly returning to its "national security" roots, as NASA plans to turn the security of the GPS system over to the Department of Homeland Security.

White House Pressure for a Donor?  The Pentagon has worried for months that a project backed by a prominent Democratic donor might interfere with military GPS.  Now Congress wants to know if the White House pressured a general to change his testimony.

LightSquared: The Next Big Obama Scandal.  The new Obama scandal is huge, but it's also nice and simple.  LightSquared is a satellite broadband company, based out of Virginia.  It received heavy investments from a fund run by a big-money Democrat donor named Phillip Falcone, a billionaire who "became wealthy shorting subprime debt," according to The Daily Beast.  The company's biggest investors, according to the Huffington Post, include Obama donor and current U.S. ambassador to South Africa Donald Gips, Obama friend and investment manager George Haywood... and Barack Obama himself...

Air Force general tells secret Congressional hearing,
White House forced me to back project funded by Obama donor.  A four-star Air Force general told a classified Congressional hearing he was pressured by the White House into changing a political briefing to favour a Democratic-backed firm.  Air Force Space Commander General William Shelton was speaking about a wireless project by Virginia satellite broadband company LightSquared.  The Pentagon believes it could interfere with GPS — but the firm's majority owner happens to be Democratic donor Philip Falcone's hedge fund.

White House Pressure for a Donor?  The Pentagon has worried for months that a project backed by a prominent Democratic donor might interfere with military GPS.  Now Congress wants to know if the White House pressured a general to change his testimony.

Advisory Board: LightSquared, GPS Can't Coexist.  On Friday [1/13/2012], two Deputy Secretaries, one at the Department of Transportation and the other at Defense, in their capacities as co-chairs of the National Space-Based Positioning, Navigation and Timing (PNT) Executive Committee, released a one page letter concluding that the modified broadband deployment plan of LightSquared could not coexist with current GPS devices and their spectrum.

FCC moves to kill LightSquared over GPS interference concerns.  The Federal Communications Commission (FCC) moved to reject LightSquared's planned wireless network on Tuesday [2/14/2012] after the president's top adviser on telecom issues said there is "no practical way" to prevent the network from disrupting GPS devices.  Philip Falcone and his investment firm Harbinger Capital invested billions of dollars in LightSquared's plan to build a nationwide high-speed cellphone network, which now appears dead.

LightSquared vows to fight FCC decision.  Wireless start-up LightSquared plans to fight the Federal Communications Commission's (FCC) move to reject its proposed nationwide 4G network, a company official told The Hill.  Jeff Carlisle, LightSquared's vice president for regulatory affairs, said the company will file a formal comment with the FCC urging the agency not to follow through on its proposal to "indefinitely suspend" LightSquared's authority to operate cell towers.

Supreme Court: Police Need Warrant for GPS Tracker.  The government argued that attaching the tiny device to a car's undercarriage was too trivial a violation of property rights to matter, and that no one who drove in public streets could expect his movements to go unmonitored.  Thus, the technique was "reasonable," meaning that police were free to employ it for any reason without first justifying it to a magistrate, the government said.  The justices seemed troubled by that position at arguments in November, where the government acknowledged it would also allow attaching such trackers to the justices' own cars without obtaining a warrant.

All Hail Samuel Alito, Privacy Champion Extraordinaire!  Yesterday [1/23/2012] the Supreme Court handed down the most important privacy case of the Roberts era, U.S. v. Jones.  The unanimous decision is an occasion for dancing in the chat rooms.  In holding that the government needs a warrant before attaching a GPS device to a suspect's car to track his movements 24/7 for a month, all the justices rejected the Obama administration's extreme and unnecessary position that we have no expectations of privacy when it comes to the virtual surveillance of our movements in public places.

Tests found major flaws in parolee GPS monitoring devices.  A little more than a year ago, California quietly began conducting tests on the GPS monitoring devices that track the movements of thousands of sex offenders.  The results were alarming.  Corrections officials found the devices used in half the state were so inaccurate and unreliable that the public was "in imminent danger."  Batteries died early, cases cracked, reported locations were off by as much as three miles.  Officials also found that tampering alerts failed and offenders were able to disappear by covering the devices with foil, deploying illegal GPS jammers or ducking into cars or buildings.

Australia's GPS Was Off Because the Whole Country Moved.  Australia is moving.  This isn't so surprising — all the continents are on the move, and Australia drifts 70 millimeters to the northeast every year.  But that journey is starting to mess with systems that rely on pinpoint accuracy, specifically GPS.  The country its currently updating its very longitude and latitude to correct a divergence with global satellite navigation systems.  Geoscience Australia, a part of the Australian government, is behind the project of getting the Geocentric Datum of Australia, the country's national coordinate system, up to code and bring it in line with international data.

The Editor says...
The GPS systems available to the general public do not offer the level of precision performance with which one would notice a movement (of everything!) of 70 mm per year.  If you're in a self-driving car, or you are landing an airplane or using GPS in any other application, you can only rely on it for relatively coarse positioning.

Semi-truck gets stranded on North Carolina beach after GPS gives wrong directions.  A truck driver took a ride on the wild side after his GPS apparently led him onto a North Carolina beach.  The driver of the Interstate Van Lines truck told WVEC-TV he was supposed to be driving south on Route 12 Monday [7/2/2018] but somehow ended up travelling north.  He tried to find a place to turn around but instead reached the end of the road — quite literally — and ended up stuck on the beach in Corolla, North Carolina, a small village in the Outer Banks.

A $225 GPS spoofer can send sat-nav-guided vehicles into oncoming traffic.  Billions of people — and a growing number of autonomous vehicles — rely on mobile navigation services from Google, Uber, and others to provide real-time driving directions.  A new proof-of-concept attack demonstrates how hackers could inconspicuously steer a targeted automobile to the wrong destination or, worse, endanger passengers by sending them down the wrong way of a one-way road.  The attack starts with a $225 piece of hardware that's planted in or underneath the targeted vehicle that spoofs the radio signals used by civilian GPS services.  It then uses algorithms to plot a fake "ghost route" that mimics the turn-by-turn navigation directions contained in the original route.  Depending on the hackers' ultimate motivations, the attack can be used to divert an emergency vehicle or a specific passenger to an unintended location or to follow an unsafe route.  The attack works best in urban areas the driver doesn't know well, and it assumes hackers have a general idea of the vehicle's intended destination.

Jeep stuck in Whately woods after GPS gives wrong directions.  If you think your GPS is misleading you, it just might be, as a newcomer to the area found out Monday [3/18/2019].  In a post on its Facebook page, the Whately Police Department shared the story of a man who a concerned Whately resident found walking along Westbrook Road.  The resident discovered that the man, who had recently moved to the area, had gotten his Jeep stuck in the woods, after his GPS told him he was on a road.

New Type Of GPS Spoofing Attack In China Creates "Crop Circles" Of False Location Data.  A new type of GPS spoofing technology, which may belong to the Chinese government, appears to have been impacting shipping in and around China's Port of Shanghai for more than a year.  Unlike previous examples of spoofing attacks, which have typically caused GPS receivers in a certain area to show their locations as being at a limited number of fixed false positions, the incidents in Shanghai caused the transponders on multiple ships at once to show various erroneous positions that forms odd ring-like patterns that some experts have dubbed "crop circles."

More information about GPS as a potential threat to privacy can be found here.

GPS background material and GPS-related web sites:

Joe Mehaffey and Jack Yeazel's GPS Information Website
Sam Wormley's Global Positioning System (GPS) Resources  (Excellent web site!)
David L. Wilson's GPS Accuracy Web Page
GPS Nuts is a web site for GPS navigation enthusiasts.
GPS Enthusiasts Web Ring - Evidently there are several such web sites.
How GPS works
GPS overview
Definitions of GPS Terms
Another GPS overview
GIS File Library
Map gallery
GPS history and theory of operation
Current GPS Satellite Data from the little-known National Imagery and Mapping Agency.
WAAS performance
Stanford University Testbed Master Station has something to do with WAAS.
Discussion of Selective Availability
NGS FAQ page Explains the difference between NAD27, NAD83 and WGS84.
Notes on GPS, Geodetic Datums, and Grid/Lat-Lon Conversions
Principles and Practice of GPS Surveying.

To see the current GPS week, among other things, go here.

GPS applications:

GPS Technology and Cars.
Rino 110:  A walkie-talkie with built-in GPS.
Garmin GPS sensors and boards.
Garmin GPS35PC TracPak, available here.
Using GPS to get Time and Frequency
Using a GPS receiver as a NIST traceable frequency reference
US Coast Guard GPS page
GPS news
Trimble Thunderbolt is used in precisely locating cell phones using Time Differential Of Arrival.

The 12 Channel Lassen IQ GPS Receiver with DGPS looks like fun
... and for only a few dollars more you can get the Evaluation Board.

This isn't the news page, but here are a couple of news items with a GPS twist:
Big Brother rides shotgun:  Rental-car company uses GPS to track customer, fines him $450 for speeding.

Galileo sat-nav system still without service.  Europe's satellite-navigation system, Galileo, remains offline.  The network suffered an outage on Friday [7/12/2019] due to what has been described as a "technical incident related to its ground infrastructure".  Engineers worked around the clock over the weekend but there is no update yet on when the service will resume. [...] Galileo is still in a roll-out, or pilot phase, meaning it would not yet be expected to lead critical applications.

Denver drivers followed Google's detour down a dirt road.  A crash on the main road to Denver's airport led to hour-long delays this week.  When Google Maps offered a quick detour, nearly a hundred drivers were led into trouble.  [Video clip]

An Introduction to GNSS.  What has most significantly changed navigation techniques is the advent of GNSS (Global Navigation Satellite Systems) which started with the launch of the U.S. Department of Defense Global Positioning System (GPS) in the late 1970's.  Early applications of GNSS were developed for the military, and in the fields of surveying and mapping.  Now, commercial operators of planes, trains and automobiles can know their position and heading quickly and accurately.

Move over, GPS.  Galileo will be Europe's own global navigation satellite system, providing a highly accurate, guaranteed global positioning service under civilian control.  It will be inter-operable with GPS and GLONASS, the two other global satellite navigation systems.  Galileo will deliver real-time positioning accuracy down to the metre range, which is unprecedented for a publicly available system.

EU Considers Running Galileo GPS Project.  The European Union is to consider taking over the Galileo satellite system as it is faced with demands for more time and extra public funds from the project's private builders, officials said.

European satellite launch challenges GPS.  The European Union launched its first Galileo navigation satellite on Wednesday [12/28/2005], moving to challenge the United States' Global Positioning System (GPS). … Galileo's accuracy in positioning is to be 3 feet or less, while GPS's precision is more than 15 feet.  EU officials also say Galileo would never be switched off for strategic reasons, which could sometimes be the case with GPS.

Europe still keen on Japan joining Galileo GPS project.  In just four years, Europe will bring about a sea change in the world of car and man navigation, which has long depended on a single service source, the American global positioning system.

EU's satellite project, Galileo, funded at last.  After hours of haggling, the European Union on Friday [11/30/2007] salvaged its highest profile investment project, agreeing to divert €2.4 billion of public money to bail out its struggling satellite navigation project, Galileo.  Designed to rival the American GPS system, Galileo has been beset by funding difficulties and hit by lengthy delays after a consortium that was supposed to get the satellite network off the ground failed to agree on financial terms.

How GPS Is Killing Lighthouses:  The popularity of the satellite-based global positioning system has led to the closure of lighthouses along the German coast.  Many more may soon be extinguished.  But critics question whether the new system is reliable and safe enough to warrant the closure of these historical beacons of safety.

Announcement of the end of GPS degradation through Selective Availability 5/1/2000.
GPS Standard Positioning Service Performance Standard (PDF)

Military GPS news:  U.S. Could Deny GPS to Taliban The Defense Department could take steps to limit the usefulness of GPS receivers in the hands of Taliban forces without affecting North American users.

The Pentagon is probably jamming GPS in Afghanistan:  The U.S. Defense Department has probably been selectively jamming signals from the Global Positioning System (GPS) in Afghanistan since the start of the air campaign [October 2001], according to nonmilitary GPS experts.

GPS flaw could let terrorists hijack ships, planes.  The world's GPS system is vulnerable to hackers or terrorists who could use it to hijack ships — even commercial airliners, according to a frightening new study that exposes a huge potential hole in national security.  Using a laptop, a small antenna and an electronic GPS "spoofer" built for $3,000, GPS expert Todd Humphreys and his team at the University of Texas took control of the sophisticated navigation system aboard an $80 million, 210-foot super-yacht in the Mediterranean Sea.

The Editor says...
It is highly unlikely that the Muslim terrorists, who live day to day in the 7th century, would suddenly acquire the 21st-century skills and equipment to pull off such a stunt.  (If the Muslim terrorists know anything about GPS navigation, it is probably from the standpoint of the end user.)  It is far more likely that the technique of locally spoofing GPS could be (and probably is already) used by the military against our enemies.

"Pardon Me, Soldier, but Would You Happen to Have the Atomic Time?"  "If GPS is disrupted or jammed, a CSAC could provide precise time to the GPS receiver to enable rapid recovery or to protect receivers from GPS spoofing, a condition where false GPS signals are broadcast to fool GPS receivers with erroneous information.  The hope is that the Soldier wouldn't even know that his GPS is being jammed."

Rocket launched into space; carries satellite to guide weapons.  A rocket carrying a GPS satellite to better guide military weapons was launched into space Thursday.  The Delta 2 rocket lifted off from Cape Canaveral at 3:04 p.m. (2004 GMT) with the modernized NAVSTAR Global Positioning System Block 2R military navigation satellite aboard for the U.S. Air Force. … The satellite is expected to circle the Earth for up to a decade before becoming obsolete.

[The article includes no mention of the price tag for ten years of service.]

Would You Track Your Kid by GPS?  Question:  if you had the ability to track your child's every movement during the day, would you do so?  Or is this an example of helicopter parenting taken to extremes?  How about tucking a portable GPS unit in her backpack?

Editorial comment:
Surfing the internet, you may find people who believe that GPS navigation is degraded or unusable in cities where there is a TV station on Channel 23 or Channel 66.  This is because Channel 23's third harmonic and Channel 66's second harmonic are in the neighborhood of the GPS downlink frequency.  Some tech writers seem to be especially concerned because the signals from digital TV stations have the same noise-like characteristics as the GPS signals.  I haven't been to such a location to check it out, but keep in mind that spurious and harmonic signals from DTV stations are supposed to be 110 dB below the power level of the station's primary output, and even at a station with a megawatt of average power, that would only leave a maximum of 10 microwatts of power in the GPS band.  That's not much power, but then again, the GPS signals are very weak, too.

Is GPS reliable?  Yes.

The news media thrive on crises and stories of impending doom.  Pay no attention when they come up with sensational predictions such as the following:

GPS System Could Fail Next Year, Report Warns.  Mismanagement and underinvestment by the U.S. Air Force could possibly lead to the failure and blackout of the Global Positioning System (GPS), a federal watchdog agency says.  The risk of failure starts in 2010, according to the Government Accountability Office (GAO) report quoted by PC World.

GPS System Could Begin To Fail Within a Year.  The Global Positioning System faces the possibility of failures and blackouts, a federal watchdog agency has warned the U.S. Congress.  Mismanagement by and underinvestment by the U.S. Air Force places the GPS at risk of failure in 2010 and beyond.  The problem:  Delays in launching replacement satellites, among other things.

Here is the "all clear" message to end this "crisis" ...
Tax GPS to save GPS?  For starters, how big a crisis is this?  Not so bad.  We really only need 24 satellites working in order to have assured accuracy, and there are 31 operational in the current constellation, with more launches planned.  The odds of seven or more failing before replacements get into orbit is rather low.  The satellites may be reaching the end of their expected lifespans, but military equipment often lasts much longer than its expected lifespan.

Don't rely too heavily on GPS -- or any computer system!

GPS mistakenly leads woman into flash floods in Catalonia, where she drowns.  A woman was swept away during flash floods in a village 45 kilometers from the Catalan capital of Barcelona in Spain after her GPS device sent her driving across a riverbed through the village of Sant Llorenç d'Hortons.  The 20-year-old woman, who was not named, was traveling with her partner to reach a caravan site where they would meet family members when the incident happened, the Local reports.

Woman Killed After GPS Takes Her to Wrong Street.  GPS directions might at times drive you insane, but one woman was actually driven to her death in Brazil.  Travel agent Regina Murmura, 70, and her husband Francisco, 69, were aiming for a Niteroi beach on Avenue Quintino Bocaiuva on Saturday [10/10/2015] when their Waze GPS app directed them to Quintino Bocaiuva Street, home to one of the city's most notorious favelas or slums, Caramujo, where drug gangs run rampant, report the Telegraph and Sky News.  There, Regina Murmura was shot as someone fired 20 bullets into the couple's car, police say.

2 bicyclists in 2 days on I-94, 1 said smartphone GPS took her there.  In the last two days, bicyclists have pedaled their way onto Interstate 94, prompting calls from concerned motorists and potentially, a hefty fine — or worse. [...] On Tuesday [6/16/2015] in St. Paul, a 14-year-old bicyclist told police she followed her smartphone GPS to eastbound I-94.  Just after 8 a.m., she was near Highway 280 when several drivers called 911.

Driver follows GPS off demolished bridge, killing wife, police say.  A Chicago woman was killed after her husband followed their car's GPS navigation off a partially demolished bridge that has been closed since 2009, according to reports.  Zohra Hussain, 51, died after their Nissan Sentra fell more than 37 feet off the old bridge and burst into flames.

Woman drives 900 miles out of her way after GPS error.  Put too much faith in technology and you may wind up in Croatia. [...] The woman only wanted to go about 90 miles from her hometown of Hainault Erquelinnes, Belgium, to pick up a friend at the Brussels train station.  Her GPS device sent her about 900 miles to the south before (during the second day of driving) she realized that something was amiss.

Australia police discourage use of Apple maps app after rescues.  Police say they have rescued a half-dozen motorists in recent weeks who were using the app to navigate to a city only to find themselves stranded in the wilderness of a national park.

Alderman Suggests Requiring GPS Devices On All Guns.  A South Side alderman is asking for City Council hearings on an unorthodox gun control measure that would allow for GPS tracking of firearms.  WBBM Newsradio Political Editor Craig Dellimore reports Ald. Willie Cochran (20th), a former police officer, has suggested that global positioning system chips be embedded in new guns, and retrofitted on existing firearms, so they could be located if they go missing.

The Editor says...
This is a remarkable display of ignorance on the part of the Alderman.  If the police wanted to locate a specific gun, the "GPS" device would have to include a cell phone, and the criminal would have to be dumb enough to leave the device on the gun, and the device would have to be in contact with a cell tower, which is easy enough for a gun owner to prevent.

GPS drivers led astray by the lights.  British motorists left frustrated when their expensive satellite navigation systems do not work now have a culprit to blame — the northern lights.  The aurora borealis, which produces colourful light displays in the sky above northern Europe, disrupts the satellite signals that satellite navigation devices rely on to pinpoint their location.

Similarly ...
Convoy rescued after GPS led them to Utah cliff.  A GPS device led a convoy of tourists astray, finally stranding them on the edge of a sheer cliff.  With little food or water, the group of 10 children and 16 adults from California had to spend a night in their cars deep inside the Grand Staircase-Escalante National Monument.

A tip of the hat to Peter G. Neumann
Homeowner Says Crews Demolished Wrong House.  A Sandy Springs [Georgia] man got a phone call Monday [6/8/2009] that his family home in Carroll County was gone.  Torn down.  Demolished. ... Channel 2 Action News reporter Jovita Moore asked Byrd if the demolition company had an address.  I said, "What address did you have?" and he said, "They sent me some GPS coordinates."  I said, "Don't you have an address?"  (and) he said, "Yes, my GPS coordinates led me right to this address here and this house was described."  said Byrd.

Woman drives into marsh on GPS advice.  The driver and her two female passengers were returning to the hotel from dinner in the Mercedes rental when they became lost and tried to use the Hertz-provided GPS.  The woman told police she was following the satellite navigator's instructions but must have made a wrong turn just after midnight on Wednesday [6/15/2011].

GPS Tracking Disaster: Japanese Tourists Drive Straight into the Pacific.  Three Japanese tourists in Australia found themselves in an embarrassing situation after their GPS navigation system lured them down the wrong path.

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Updated November 21, 2019.

©2019 by Andrew K. Dart