The closeness of a repeated set of observations of the same quantity to one another.

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175
votes
5answers
138k 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 ...
10
votes
2answers
1k views

What is the precision of SELECT DISTINCT on PostGIS geometry column?

I wonder what the precision of the SELECT DISTINCT operator is on a PostGIS geometry. On my system, the following query gives me a count of 5, which means that the inserted points are considered equal ...
9
votes
2answers
7k views

Low-cost centimeter-level accurate satellite positioning (GNSS/GPS) [closed]

I am looking for a low-cost (< US$500) GNSS/GPS setup with a centimeter precision without much HW hacking. I am not able to produce my PCB or do any soldering (though I would do that if there is no ...
7
votes
4answers
866 views

Precision vs Resolution in elevation data

Update: A good example of something I am confused about: on the Wikipedia page for "digital terrain model" one can find the following statement about a satellite in the "See Also" section: ...
7
votes
2answers
9k views

Creating DEM from point data in CSV files using ArcGIS Desktop?

I have a lot of csv files which contain point data containing height, aspect and slope measurements at a resolution of 12,5 meters. I need to create a dem from this data and have ArcGIS 10 with ...
6
votes
1answer
773 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 ...
5
votes
1answer
2k views

What is the precision of a Geohash

I would like to know the precision of a geohash with a given length. If there is a 'simple' formula you can use to calculate it, that would be extra-cool. Wikipedia lists the precision up to 8 ...
5
votes
2answers
1k 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 ...
4
votes
4answers
3k views

ArcGIS 10 exports losing precision with large numbers

I wonder if anyone else has run into this problem; and I'm baffled as to its reason and solution. Whenever I do an export of features that have large-number attributes (over 14 digits) to a ...
4
votes
1answer
299 views

Display XY Format to Shapefile (Scale)

Using ArcView 10.1 and using excel for Lat/Long conversion to a shapefile. The original Lat/Long has 7 numerical characters past the decimal point xx.1143717. When I convert this excel into a ...
3
votes
2answers
67 views

Compensating lat/long offsets after conversions

In my application I am doing conversions between two different formats of data. First format is a simple one containing NE and SW coordinates for a given rectangular area: area = { "sw": { ...
3
votes
1answer
89 views

What are arc's guarantees on data precision, XYTolerance (i) when displaying (ii) in arcpy?

Interesting behaviour: Two line segments in a dataset have almost, but not quite, identical endpoints. The difference between them is less than the XYTolerance for the data set. Reading the ...
2
votes
1answer
136 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
2answers
108 views

Is this distribution of GPS positions caused by multipath distortion?

I have some GPS points that are close to where they should be, but not nearly close enough (horizontal precision is around 10 meters). Looking at the positions which comprise these points (there are ...
2
votes
2answers
223 views

How to handle coordinates accuracy in ArcGIS

I am creating very basic rectangular polygon using very basic a Python code nCols,nRows=100,100 corners =[[0,0],[0,nRows],[nCols,nRows],[nCols,0],[0,0]] ...
2
votes
0answers
25 views

Do somebody know how factors as “age of data”, “scale” and others influence the precision of GIS data?

Several factors may cause imprecision in datasets. As example of such sources, we should list: "age of data", "formatting", "scale", the technique employed to create the data and others. Each of them ...
2
votes
0answers
149 views

Row.Value returns rounded SHAPE.area and SHAPE.len values

I have created a VB.Net Add-In, and am using IRow to get the value of fields in tables in ArcMap to use in a query. But I am encountering a problem when getting the values of the SHAPE.area and ...
2
votes
0answers
187 views

Spatial Precision for Editing in Multiple GIS Clients

I have something I'd like to discuss, I'll try to explain it first, why it's important, and I'll explain how ArcGIS handles the issue, which I think is a good way to handle it. Finally I'd like to ...
1
vote
3answers
4k views

How to auto fill or delete sliver polygons without losing precision?

I am developing some boundaries in which precision holds the key value. Using ArcGIS 9.3 I am converting lines to polygons using the "feature to polygon" tool. The lines are accurate but I find ...
1
vote
1answer
82 views

Understanding precision of ArcGIS geodatabases?

I would like to know how precision is handled in ArcGIS software. Is it using a real Computer Algebra System engine, an arbitrary precision library or do others tricks to handle precision ?
1
vote
1answer
45 views

Transfer from Android phone to Windows OS truncates lat long

I am clicking GPS enabled pictures of sites which are less than 500 metres apart through Android based Samsung ACE Duos phone. I later use Google Earth on my Laptop to view these geo tagged pictures. ...
1
vote
1answer
122 views

Unable to select FLOAT precision when adding column

I'm trying to do the lessons in the training-manual at qgis.org. I,m having some problems with 3.3 Ratio Classification ...
1
vote
1answer
293 views

PyQGIS export to JSON: writeAsVectorFormat and precision

In my QGIS plugin qgis2leaf I am exporting all layers as JSON into a JSON directory. Therefore I would like to enable the user to define the precision in the GUI. The normal "save as" dialogue in QGIS ...
1
vote
2answers
218 views

Densify a JTS LINESTRING (add points)

I have a LineString I would like to "soften" in a way that if two coordinates (vertices) in the LineString are very far apart, I want to automatically add some coordinates in between. The line ...
1
vote
0answers
24 views

Degree Precision vs. Length [duplicate]

https://en.wikipedia.org/wiki/Decimal_degrees I found this chart in one of the questions here. Additional to this: When making a measurement and getting 2 Measures of Latitude, for example ...
1
vote
0answers
44 views

FME: floating point precision issues (ArcSDE / FGDB)

I am working on a (generic) FME Workbench that clips and exports data from ArcSDE database into the File Geodatabase (FGDB) format. The SDE features are clipped using an AOI, that arrives in the ...
1
vote
0answers
35 views

How to Change Precision of Export / Add Geometry Columns field

I would like to display the coordinates of a number of points on a map. I can use Vector > Export / Add Geometry Columns which adds coordinates to 6 dp. However as I am using a UTM-type projection ...
1
vote
0answers
90 views

Precision of conversion from WSG84 to ECEF and ECEF to ENU?

To convert from a global to a local coordinate system, I apply the following transformations. WSG84 to ECEG: with and ECEF to ENU: Let's assume that the semi-major axes a and e are known ...
1
vote
0answers
189 views

Reduced real-type numbers in QGIS?

I have a SHP point file created from CSV with QGIS 2.4.0 Chugiak. It contains some data on noise in a certain point. When I import from CSV, it seems to be fine, but when I export to SHP and open the ...
1
vote
0answers
28 views

calculation precision during projection transformation

I am using wgs 84 base tiles, and the tile is not rendered as image but with geojson format. I try to draw them in the tile according to the data. And the geometry of the returned feature is lng and ...
1
vote
0answers
678 views

Precision for an FGDB raster dataset?

I would like to know the precision for an ArcGIS raster stored within a file geodatabase (FGDBR format); I can't seem to find this information anywhere in their documentation (apologies if I have ...
0
votes
1answer
1k views

How can I change the precision in the attribute table? [duplicate]

I'm working with QGIS, v. 2.0.1. I opened a csv-table (from an Excel-file) and now the precision is very high but I don't need this. At the moment the values are for example 15.00000000000000, how ...
0
votes
0answers
76 views

Why is ArcGis change precision of double field after copy?

I create the attribute table of a shapefile and while I copy it by using the "copy features" tool it change the precision from 11 to 14. I create two fields with the name poly_x and poly_y and they ...
0
votes
0answers
106 views

Calculate coordinates with better precision in ArcGIS for Desktop?

I'm using the geometry calculator to get the geographic coordinates of a point shapefile. However when I run it, it calculates the coordinates with 4 decimal points, regardless I've chosen double an ...
0
votes
0answers
36 views

A machine to measure latitude to 6 decimal places of a degree [duplicate]

I am doing a PhD research project to do with medieval and ancient archaeoastronomy which requires me to be able to measure latitudes up to an accuracy of 6 decimal places of a degree of latitude. ...