1
vote
1answer
38 views

Accuracy issues between data in QGIS and Google Earth

Wondering if anyone can answer this question. I have a kml in Google Earth. When I import it to QGIS, and then import the Google Earth images they are in slightly different places. I used a QGIS ...
3
votes
1answer
69 views

If the GPS navigation message takes 12 1/2 minutes to cycle, how can receivers update your position every second?

According to Wikipedia's article on GPS, Each GPS satellite continuously broadcasts a navigation message... Each complete message takes 750 seconds (12 1/2 minutes) to complete. My ...
5
votes
2answers
503 views

Accuracy vs Precision GPS

I am doing some research on consumer grade GPS accuracy and precision. I took 5 readings for 20 known locations (100 readings). Am I correct in assuming that the standard deviation between the 5 ...
2
votes
2answers
655 views

What class/types of smartphone chipsets support GPS, A-GPS, GLONASS AND have extended kalman filtering?

I've been testing several Android phones (all running Android 4+) Sony Xperia T, Moto G, Nexus and HTC 1 which are all giving decent tracks (all of which use GPS/GLONASS) However we are also using ...
4
votes
1answer
274 views

What is required for post-processing differential correction? (And can Garmin units provide it?)

2 very closely related questions about differential correction with a Garmin unit: 1). Some data was collected using a Garmin GPSMAP 76Cx unit and the data collectors are interested in whether ...
2
votes
1answer
150 views

Is there any information in Sky Plot that is not in DOPs chart in terms of predicting accuracy in the field? (GPS data collection planning)

Joe only looks at DOPs chart and weather report for mission planning. Moe looks at both DOPs chart and Sky Plot and weather report. Is Joe missing out on something relative to Moe in terms of ...
2
votes
1answer
92 views

What is a reasonable time to get a gps fix with 10 meters precision?

I hope I'm asking this at the right part of Stack Exchange. Please bear with me if I'm wrong. I'm developing some gps based applications. The demands I have for precision are not very high, but I ...
4
votes
1answer
146 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 ...
14
votes
3answers
11k 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 ...
11
votes
1answer
579 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
410 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 ...
31
votes
12answers
20k 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
779 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
1k 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 ...
23
votes
6answers
797 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
2k 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
2k 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 ...