Tagged Questions

0
votes
0answers
24 views

Best handheld GPS unit under $500? [duplicate]

I hope this is okay to post here. I want to do some data collection in my free time which will be hosted on my own website for people to freely download and use. I obviously want the data to be as ...
4
votes
1answer
76 views

GPS Elephant Tracking II: Is ArcGIS basemap imagery orthorectified?

-- For my original question and pictures of elephants wearing GPS equipped anklets, go here. -- I'm experimenting with the use of GPS anklets to track the movement of zoo elephants. This has proved ...
11
votes
3answers
2k views

What is the maximum Theoretical accuracy of GPS?

I was talking with a potential client, and they requested that we plot some points with GPS, with a maximum (or should that be minimum?) accuracy of 2 m. This is an area with no WAAS, and I was under ...
8
votes
1answer
331 views

How much sense does it make to average (lat,lon) samples in order to increase 2D accuracy of a GPS location?

Several GPS applications, like this one, or this one, acquire multiple (lat,lon) samples of a given location, assuming that the GPS unit is not moving, and then take an average of the samples in order ...
19
votes
2answers
340 views

Precision when working with spatial data in GIS

Is there a basic or introductory study that examines and compares the precision of spatial data when working with varying precison of the data input, like having 1, 2, ... decimal places? with the ...
24
votes
11answers
10k views

Tablet or smart phone GPS vs “real” GPS

I've been reading a lot today about android and iphone devices being used for spatial data collection in the field and it sure seems to be that single purpose devices such as the extremely popular ...
12
votes
3answers
452 views

GPS Elephant Tracking: Utilizing A-GPS, WAAS, DGPS and Understanding HDOP, NSAT, and ZDA

*I'm using a GPS data logger (qstarz bt-q1000xt) to track the movement of zoo elephants, and I have a variety of technical questions. I've had limited success receiving answers from the vendor. You ...
2
votes
1answer
730 views

how to calculate RMS 2D and RMS 1D, using python?

I would like to calculate: RMS 2D: standard deviation for the two coordinates of flat (67% confidence level) and RMS 1D: standard deviation for height (67% confidence level) What is the formula and ...
24
votes
6answers
725 views

How to cope with the newly discovered GPS bug? [closed]

Today the New York Times broke the news that after the Clinton Administration turned off Selective Availability in the GPS system, a bug had been introduced into the GPS satellite software itself, ...
17
votes
6answers
1k views

How correct is the “Accuracy” value given by GPS devices?

I have a Garmin Forerunner 305 and a Google Nexus One Android phone. From the GPS on both these devices I can get a "Accuracy" value that is usually between 6-20 meters. How much can I trust this ...
18
votes
6answers
1k views

Is GPS more accurate on specific hours of the day?

I have heard that the GPS system is more accurate, and less accurate on some specific hours on the day. If this is true, how can I get the information on when GPS is more or less accurate at my ...