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

learn more… | top users | synonyms

1
vote
1answer
333 views

How geographically accurate is Google Earth?

I'm using a KML file which I have loaded in to Google Earth. I am looking at some islands, and see items such as the following island: Note the blue region is the polygon describing the area ...
2
votes
1answer
132 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 ...
2
votes
0answers
402 views

How to use QGIS Accuracy Assessment plugin? [closed]

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: ...
5
votes
2answers
276 views

Spatial interpolation - appropriate method to estimate the accuracy of the surface

When using a spatial interpolation method (any method) without having a way to validate it, besides sampling some points out, is there a way to count as well with the mean distance between ...
2
votes
1answer
7k views

How accurate is the google maps latitude and longitude I am using?

I am making a program that uses GPS location preferably from smart phone, laptop works too and compares it to a building, the points you in its general direction. I am making this web application ...
4
votes
1answer
254 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 ...
3
votes
2answers
314 views

How to get the best accuracy of coordinates for web GIS- application?

I would like to get advice from you about one thing. I would like to develop my own web GIS application. It would be about some sport places in my hometown; it would be good practice for my education ...
20
votes
5answers
31k 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 ...
3
votes
1answer
222 views

CORINE LandCover: what about the accuracy?

How accurate is CLC? Do anyone know any scientific papers about that question? I tested the new CLC2006 for a region in turkey and its totally rubbish!
13
votes
2answers
971 views

ArcGIS Buffer accuracy problem?

Once again I encounter something very strange with ArcGIS. I perform a buffer analysis on one side of a polyline. There seems to be a serious accuracy problem and I can't figure out what the cause is. ...
2
votes
1answer
429 views

How do you calculate positional accuracy in qgis?

How to you compare two layers in QGIS to get the positional accuracy?
6
votes
1answer
736 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 ...
14
votes
2answers
2k 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 ...
31
votes
2answers
4k 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 ...
4
votes
1answer
1k views

Probability of iOS/Android device location accuracy

I'm working with Android and iOS apps that report location. Both iOS and Android can derive location from a combination of cell tower triangulation, visible wifi access points, and assisted GPS. The ...
19
votes
2answers
472 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 ...
34
votes
12answers
29k 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 ...
4
votes
1answer
731 views

Does a geotagged image contain information about its accuracy?

When i view my current location on Google maps on my android it shows me a circle of uncertainty. If i take a geotagged picture it will off course contain information about its Lat or Lon. Does it ...
4
votes
1answer
644 views

Which interpolation method is the most suitable for DEMs?

Which interpolation method is the best suitable for hill/valley areas and normal ground with undulations and rivers? When working with Aster 30mX30m DEMs, which method will give the most realistic ...
6
votes
1answer
360 views

How to store Large Raster Images of Equipotential Surface Generation Using Monte Carlo Simulation?

I have a large (1GB+) raster that I am using as the base for the generation of an equipotential surface. This is to assess the accuracy of DEMs derived from another source. In situ observation is ...
12
votes
3answers
1k 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
2k 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 ...
4
votes
4answers
240 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
338 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
7k views

How accurate are measurements in Google Earth?

Can anyone point to a resource that lists the accuracy of measurements taken in Google Earth?
9
votes
3answers
12k 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 ...
149
votes
5answers
124k 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
833 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
282 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
143 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 ...
19
votes
5answers
4k 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
7k 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, ...
21
votes
6answers
4k 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 ...