GPS Lat Lon

[briansue]

DECIMAL DEGREES

Decimal degrees are an alternative to using degrees, minutes, and seconds (DMS). As with latitude and longitude, the values are bounded by ±90° and ±180° respectively. Positive latitudes are north of the equator, negative latitudes are south of the equator.

We recently went to the movie “Hidden Figures”. I noticed they used Decimal Degrees for the math they use to determine where and how to get the first manned satellites back to earth. They could determine where the splashdown would occur. I am not sure how long Decimal Degrees has been around. I have been using Decimal Degrees for quite a while simply because it seems easier to write than other forms of Latitude Longitude formats. I know there are formulas and math and opinions vary. My main reason for using Decimal Degrees is simply ease of writing. I don’t know much about any of this but I did use Degrees, Minutes, Seconds when boating a long time ago. GPS and modern science has provided new tools.


Here is a website that has a calculator for converting different Lat Lon formats. They also have some explanations of Lat Lon formats.

http://www.earthpoint.us/Convert.aspx


The further the Lat Lon numbers are carried out – number of spaces after the decimal – the more accurate the location. Here is a chart I found estimating accuracy as number of places increases…..

Decimal
places….degrees…………distance (accuracy)
0………….1……………….111 km
1………….0.1……………..11.1 km
2………….0.01…………….1.11 km
3………….0.001……………111 m
4………….0.0001………….11.1 m
5………….0.00001…………1.11 m
6…………0.000001…………11.1 cm
7…………0.0000001………..1.11 cm
8…………0.00000001………1.11 mm
In other words theoretically 5 spaces would be close to 1 meter of accuracy.

Some ways Lat Lon can be written….
Google Earth uses the WGS84 geodetic datum. Valid formats include:
Degrees Minutes Seconds N43°38'19.39" W116°14'28.86"
Degrees Minutes Seconds 43°38'19.39"N 116°14'28.86"W
Degrees Decimal Minutes 43 38 19.39 -116 14 28.86
Decimal Degrees 43.63871944444445 -116.2413513485235
If expressed in decimal form, eastern longitudes are positive, western longitudes are negative.


Other ways Lat Lon can be written…….

27.963311 -111.024493
Calculated Values - based on Degrees Lat Long to seven decimal places.
Decimal Degrees 27.9633110, -111.0244930
Degrees Decimal Minutes 27°57.79866', -111°01.46958'
Degrees Minutes Seconds 27°57'47.9196", -111°01'28.1748"
UTM 12R 497590mE 3093138mN
UTM centimeter 12R 497590.97mE 3093138.39mN
MGRS 12RVR9759093138
Grid North 0.0°
GARS 138KV23
Maidenhead DL47LX71BE46
GEOREF EHJN58535779GEOREF EHJN58535779

[briansue]

It seems it won’t be too much longer until we will see greatly improved GPS accuracy in consumer level devices – even phones…….

GPS Tracking Down to the Centimeter

Technology developed at UCR will be used for high precision positioning in mobile devices, autonomous vehicles and related applications

https://ucrtoday.ucr.edu/34932

Researchers at the University of California, Riverside have developed a new, more computationally efficient way to process data from the Global Positioning System (GPS), to enhance location accuracy from the meter-level down to a few centimeters.

The optimization will be used in the development of autonomous vehicles, improved aviation and naval navigation systems, and precision technologies. It will also enable users to access centimeter-level accuracy location data through their mobile phones and wearable technologies, without increasing the demand for processing power.

“Achieving this level of accuracy with computational loads that are suitable for real-time applications on low-power processors will not only advance the capabilities of highly specialized navigation systems, like those used in driverless cars and precision agriculture, but it will also improve location services accessed through mobile phones and other personal devices, without increasing their cost,”
MORE ONLINE

Cheap Centimeter-Precision GPS For Cars, Drones, Virtual Reality

http://spectrum.ieee.org/tech-talk/transportation/self-driving/cheap-centimeterprecision-gps-for-cars-and-drones


Engineers at the University of Texas at Austin have now made a small, cheap GPS system for mobile devices that gives centimeter-precision positioning accuracy. Such centimeter precision could let drones deliver packages to your porch, autonomous vehicles navigate safely, and be used in precision farming. It could also allow for some neat virtual reality tricks and games if coupled with a smartphone camera, says Todd Humphreys, an aerospace engineering researcher at UT Austin. “People could have an engaging mind-blowing experience with physically immersive virtual reality,” he says.


For those want to see the scientific explanation…..

Accuracy in the Palm of Your Hand

http://gpsworld.com/accuracy-in-the-palm-of-your-hand/

Centimeter Positioning with a Smartphone-Quality GNSS Antenna

The smartphone antenna’s poor multipath suppression and irregular gain pattern result in large time-correlated phase errors that significantly increase the time to integer ambiguity resolution as compared to even a low-quality stand-alone patch antenna. The time to integer resolution — and to a centimeter-accurate fix — is significantly reduced when more GNSS signals are tracked or when the smartphone experiences gentle wavelength-scale random motion.

[briansue]

I think GPS won't do much better than 10-20'.

I think that depends entirely on the GPS. Maybe our everyday Garmin or whatever is not that accurate - I don't think they have even 5 digits - but there are more accurate GPS units and there are ones that carry the digits out much further - like 6, 7 , 8 I think - which can get pretty darn accurate. Many things have to be in line - and the receiver you use has to be picking up enough satellites to get that degree of accuracy. Sometimes we see only 4 satellites on our display but we have gotten up to 11 and I would guess getting more could be possible. Though Google Earth is not a GPS it seems they can get 6 digits. But since we are RVers we do not need that degree of accuracy so we are not going to spend what it might cost to get a device that is that accurate. Below gps.gov claims they can get under 10' accuracy 95% of the time with a high quality unit - and even down to centimeters and millimeters. I wonder what one of those costs. The fact that we are pretty darn close most of the time tells me we can get as close as we will ever need. A GPS used for survey equipment can run over $5,000.


Official U.S. government information about the Global Positioning System (GPS) and related topics

http://www.gps.gov/systems/gps/performance/accuracy/


The actual accuracy users attain depends on factors outside the government's control, including atmospheric effects, sky blockage, and receiver quality. Real-world data from the FAA show their high-quality GPS SPS receivers attaining better than 2.168 meter horizontal accuracy, 95% of the time.

Higher accuracy is attainable by using GPS in combination with augmentation systems. These enable real-time positioning to within a few centimeters, and post-mission measurements at the millimeter level.

[pconroy328]

briansue wrote:

In other words theoretically 5 spaces would be close to 1 meter of accuracy.

Just a quick mention about significant digits. Beware false precision. Just because a device displays 5, 6 or more digits after the decimal point - doesn't mean it's more accurate.

I think GPS won't do much better than 10-20'.

[briansue]

As far as finding places with GPS and the accuracy of some of the coordinates listed on websites or wherever - we almost always look at Google Earth to see where the numbers put us as we have learned lots of numbers can be way off. Sometimes they are entered incorrectly and one off number can put you in the next county. We also use Google Earth to look at lots of other things such as planned fuel stops to see if we can get in and out - and how to get in and out. Never trust Lat Lon numbers without trying to check for accuracy. We also never blindly follow GPS. With GPS and Google Earth and all the other technology we have today we no longer need charts as we did when boating. We just put in the numbers and check the route and take a look on Google Earth. I think old Columbus would be so amazed his brain would explode.

[GordonThree]

2oldman wrote:
I think DMS is extremely cumbersome.

Same here... Decimal degrees all the way

[2oldman]

I think DMS is extremely cumbersome.

[Second_Chance]

Canadian Rainbirds wrote:
And while we are on the GPS topic, why do so many RV Parks list their lat and long position as the middle of the park or the office and not at the entrance? Several times the GPS has tried take us to the back street or side street.

I don't know the answer to this question, but I like the way military FamCamps' coordinates are listed on militarycampgrounds.us and the MWR web sites. They often (nearly all the time if the FamCamp is located on the post or base rather than out at a lake or off-post/base) list the coordinates for both the FamCamp and the gate specified for RV use. These coordinates are also listed in decimal degrees which make them much easier to enter into a GPS without converting them. Very handy!

Rob

[Canadian_Rainbi]

And while we are on the GPS topic, why do so many RV Parks list their lat and long position as the middle of the park or the office and not at the entrance? Several times the GPS has tried take us to the back street or side street.

[Canadian_Rainbi]

Now that is very useful information. I have been hanging on to Minutes and Seconds because it is very easy to see the distance as long as you are comfortable with Nautical Miles which of are 1 minute of latitude. The most useful to me was one second being about 606 feet, or 56 meters.

Now that we are dealing with kilometers and meters the decimal make it even easier