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

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8
votes
2answers
47 views

What is a good metric for mapping accuracy

I have recently received a dataset that supposedly mapped the altitude a given region (a DEM). I would like to determine the accuracy of the new map by comparing it with a previously generated DEM. ...
1
vote
0answers
27 views

Translating hdop, pdop and vdop to metric accuracy from given NMEA strings

How can I translate dilution of precision to a metric unit? For example: say I got 1.2 in hdop from NMEA sentence of my GPS receiver, in what should I multiply to get a metric accuracy? Just like the ...
3
votes
2answers
46 views

How are kappa and overall accuracy related with respect to thematic raster data?

I recently calculated kappa (using confusionMatrix{caret} in R) between a thematic raster dataset at 1m spatial resolution and another at 30m spatial resolution. I was interested in quantifying the ...
1
vote
0answers
19 views

Question about projected coordinate systems 30m DEM for Contiguous US

What is the best Projected Coordinate System (PCS) for the contiguous US (whole, not parts) if I want to maintain distance and area accuracy as much as possible across a nationwide DEM dataset? I'm ...
2
votes
1answer
56 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 ...
4
votes
1answer
83 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 ...
0
votes
1answer
32 views

Clip a shapefile based on raster extent with high accuracy

I am trying to clip a shapefile based on the extents of a smaller raster. I find the extent of the raster using this code: Extents = arcpy.sa.Raster(MyRaster).extent` Then, I use these lines to ...
3
votes
1answer
57 views

Map accuracy assessment by moving window in R

I would like to make an accuracy assessment using a confusion matrix between classified Landsat image and reference dataset. Maps have the same resolution and extent. I would like to evaluate the ...
1
vote
1answer
63 views

What sub-meter geolocation solutions exist and how can I integrate them into a web and mobile mapping workflow?

I am the manager of seven water systems. What I am trying to do is map out every meter and valve on to a map and then my workers can have the maps on their iPhones so when they have to go fix a water ...
5
votes
2answers
512 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 ...
1
vote
2answers
137 views

Canada FSALDU 6-digit Postal Code Data Providers

I have been looking into finding point data for the Canadian 6-digit postal code (FSALDU). I have come up with 3 sources so far, 2 being far more expensive than the other. After speaking with the ...
2
votes
2answers
838 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 ...
2
votes
1answer
268 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 ...
5
votes
1answer
323 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 ...
0
votes
0answers
111 views

Accuracy problems with Openlayers\Openstreetmap\AnimatedCluster

I am working on a OSM map that clusters several points with a modification of AnimatedCluster (https://github.com/acanimal/AnimatedCluster). However, somewhere the accuracy seems to lack. Can ...
2
votes
0answers
47 views

Is there any statistical method to proof if the method is suitable or not [closed]

I have recently done a phenological study using threshold method from MODIS NDVI images. But I'm suffered that I don't have any situ observation (ground truth) data to do validation. Is there any ...
2
votes
1answer
162 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 ...
1
vote
1answer
51 views

resampled thematic map accuracy

I've generated a map of ecoregions based on some environmental data using a semi-supervised classification where I combined a statistical clustering with random forests to generate my map. I created ...
1
vote
1answer
152 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
94 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 ...
0
votes
0answers
146 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: ...
3
votes
2answers
115 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
2k 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
152 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
224 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 ...
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 ...
3
votes
1answer
139 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!
12
votes
2answers
695 views

ArcGIS Buffer accuracy problem

world, 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 ...
2
votes
1answer
286 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
443 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 ...
11
votes
1answer
586 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 ...
24
votes
2answers
2k 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
616 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
414 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
21k 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
434 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
483 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 ...
5
votes
0answers
278 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
798 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 ...
4
votes
4answers
222 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
240 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?
6
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 ...
75
votes
4answers
45k 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 ...
23
votes
6answers
803 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
270 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
126 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
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, ...