The degree of closeness of measurements of a quantity to that quantity's actual value

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73
votes
3answers
42k views

How to measure the accuracy of latitude and longitude?

I am very new to GPS stuff. Suppose I have latitude and longitude as 19.0649070739746 and 73.1308670043945 respectively. In this case both coordinates are 13 decimal places long, but sometimes I also ...
24
votes
2answers
1k views

How accurate is approximating the Earth as a sphere?

What level of error do I encounter when approximating the earth as a sphere? Specifically, when dealing with the location of points and, for example, the great circle distances between them. Are ...
9
votes
3answers
5k views

How does ArcGIS compute the distance between two points with a non-equidistant projection?

This is a follow-up question to my previous one, Can you suggest some well-written introductory texts about coordinate system projections? Let's assume I'm working with the CH1903 map projection, ...
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 ...
0
votes
0answers
140 views

How to use QGIS Accuracy Assessment plugin?

I am new user and i want perform accuracy assessment in qgis. I have 1 classified map and another for validation. I have installed the plugin. what am i doing after? Plugin: ...
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 ...
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 ...
5
votes
3answers
6k views

Generally accepted root mean square (RMS) error for rectifying topographic maps

This is a generic inquiry on the common practice/standard for determining the acceptable values of RMS when georeferencing topographic maps. Is there an absolute value? Some literature suggests that ...
12
votes
3answers
778 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 ...
6
votes
1answer
437 views

Need to learn more about Precision and Accuracy

I am currently taking Introduction to Image Interpretation online and there is a section in it that talks about Precision and Accuracy. I wanted to know if someone out there has any good information ...
2
votes
1answer
238 views

Google earth, google satellite and bing aerial accuracy

Does anybody know what is the accuracy on Google earth, google satellite and bing aerial and on what scale.I think that you have different-better accuracy if you have subscribed to their professional ...
2
votes
1answer
279 views

How do you calculate positional accuracy in qgis?

How to you compare two layers in QGIS to get the positional accuracy?
9
votes
2answers
3k views

How accurate are measurements in Google Earth?

Can anyone point to a resource that lists the accuracy of measurements taken in Google Earth?