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

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4
votes
4answers
226 views

Is city-supplied GIS data sufficient for transit operators or do they need their own set of GIS data?

City GIS data is usually built in a format where streets/avenues/boulevards/etc are modeled as lines that are geographically located in the middle of the streets/avenues/boulevards/etc. Is that ...
6
votes
1answer
265 views

Accuracy of planimetric geometry vs. ellipsoidal model

I'm examining the two geospatial options for IBM's DB2 database. In particular I am interested in the accuracy between these two options and whether it's worth it (the more accurate representation ...
9
votes
2answers
4k views

How accurate are measurements in Google Earth?

Can anyone point to a resource that lists the accuracy of measurements taken in Google Earth?
7
votes
3answers
7k 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 ...
91
votes
4answers
67k 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 ...
22
votes
6answers
813 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, ...
4
votes
2answers
271 views

Is there a way to distinguish data precision in KML?

Here's my problem (and I was inspired to ask this from this question)... I create a KML file recording where upcoming training courses will be for the next year. The cities might be Atlanta, Calgary, ...
3
votes
1answer
129 views

What sample size should be used when applying the National Standard Spatial Data Accuracy (NSSDA)?

I'm less interested in what is recommended by FGDC, and more interested in information like this: SAMPLE SIZE AND CONFIDENCE WHEN APPLYING THE NSSDA, which suggests you need a sample of 100. Is there ...
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 ...
9
votes
3answers
6k 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, ...
19
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 ...