0
votes
1answer
94 views

ArcGIS Conversion Error While Converting ED50 Datum to WGS84 Datum

With ArcGIS for Desktop, I tried a datum conversion of Transverse Mercator ED50 Datum to Transverse Mercator WGS84 Datum. Normally, the difference between two projections is approximately 180 meters ...
0
votes
0answers
27 views

Comparing datums with GDAL/OGR

I have a bit of code in Java that takes in a SpatialReference object and checks that it is one of the acceptable datums (WGS84, NAD83, NAD83 HARN, NAD27), but because of the lack of standardization in ...
0
votes
1answer
21 views

NAD conversion in Mexixo

I am looking for the file "Mexico.gsb" which used with ArcGIS when datum shifting from NAD27 to NAD83 in Mexico.
3
votes
1answer
121 views

Why not measure elevation from the center of the earth?

In trying to understand Geoid vs Ellipsoid height, I ran across this page. One of the claims is: Zero elevation as defined by Spain is not the same zero elevation defined by Canada ...
0
votes
1answer
70 views

Persistent datum conflict error. Datums are the same

I'm clipping a number of features using other feature layers, and was careful to get everything into WGS84 beforehand, using what I thought were the proper datum transformations. Now I keep getting ...
0
votes
0answers
104 views

Myanmar Datum 2000 information

Does anybody know where I can find the technical details for Burma's latest datum? It's called Myanmar Datum 2000 and I can't find any details online. I need the details to create a custom datum on my ...
3
votes
2answers
53 views

What is the closest CRS to “Meridiano de Greenwich”

I have a 1906 scanned map that I am trying to georeference in QGIS for Mac. The map has French and English lat-long, indicating them as either "Meridiano de Greenwich" or "Meridiano de Paris." I would ...
1
vote
1answer
152 views

datum conversion with GDAL

I run gdaltransform like so: gdaltransform -s_srs nad27 -t_srs wgs84 -104.5 39.5 -104.5 39.5 0 gdaltransform -s_srs wgs84 -t_srs nad83 -104.5 39.5 -104.5 39.5 0 gdaltransform -s_srs nad27 ...
2
votes
1answer
467 views

What is the process to calculate Helmert parameters?

I have some double points (the same points in 2 different datums). I'd like to calculate the Helmert parameters but I don't understand how. NOTE: I don't need software. I need an algorithm in order ...
2
votes
1answer
99 views

What do different realizations of the same datum have in common?

Firstly, am I correct in assuming that the process of determining the shape and the size of the spheroid is independent from the process of determining the origin and the orientation? For example, ...
4
votes
2answers
78 views

towgs Definition for European Datum 1950

I am new to all things GIS so apologies for a basic questions. I am trying to specify the CRS of a climatic raster layer in R. It is an equal area projection based on Europe Equidistant Conic and the ...
2
votes
1answer
28 views

IL East 1201 coordinate system

What is the difference between NAD CORS96 (Illinois East 1201) and the "normal NAD1983? We have data that was GPS'ed in CORS96, but data was imported into ArcMap using the "normal" NAD1983? What ...
0
votes
1answer
82 views

RFE raster images datum conflict

Im using ArcGIS 9.3. I've downloaded RFE images from FEWSNET. And im trying to load them on ArcMap, to clip them using Mozambique's shape. But as the RFE images related to Southern Africa come with ...
5
votes
1answer
100 views

Is there a way to determine the datum used when all you have is a lon and lat?

I have a dataset of US intersections from 2011 that I'm going to be using in a project together with data based in WGS84. Included in the CSV file is a variety of fields two of which are the lat and ...
2
votes
2answers
233 views

Older British Geological Survey geology maps of Kenya; need complete projection information

I have several geologic maps of Kenya produced by the BGS circa 1993. Noted on each map is the following: Projection:-Transverse Mercator Spheriod:-Clarke 1880 (modified) That's great, but that ...
1
vote
1answer
36 views

Datums in compound CRSs

Is there some specific constraint regarding vertical and geodetic datums within a compound Coordinate Reference System (CRS)? E.g. if the ellipsoid model should be the same or not, or if the vertical ...
3
votes
2answers
566 views

Where is list of Geographic Transformations in ArcGIS, and their areas of applicability?

I have some data in Provisional South American Datum 1956, and I need to project it to Web Mercator with WGS84 as the datum. When I use the project tool in ArcGIS desktop, it requires a Geographic ...
1
vote
1answer
137 views

Modify CRS to match boundaries of shapefile

I have boundary data in WGS'84 lat/long and data in a custom generated CRS. The data in the generated CRS appears to be offset by a particular vector compared to WGS'84. I want to attempt to match the ...
0
votes
0answers
106 views

How to determine Earth co-ordinates?

I just read about latitudes and longitudes. I read latitudes are imaginary lines that run around the earth and longitudes are lines that run around from top to bottom. Using this system: 1. ...
20
votes
1answer
4k views

Is WGS84 itself a Coordinate Reference System?

I was wondering the difference between WGS84 and EPSG:4326 (see this). Can then WGS84 on its own be defined as a Coordinate Reference System? Or is it just a datum so that a Coordinate System must ...
1
vote
1answer
338 views

What datum (reference ellipsoid) does Nasa Worldwind use?

What datum (reference ellipsoid) does Nasa Worldwind use? I can't seem to find where Nasa Worldwind tells explicitly what datum they use. I need some sort of valid link.
42
votes
7answers
3k views

What strategies, criteria, or rules to use for selecting coordinate systems?

What strategies, criteria, or rules do you use for selecting coordinate systems for (a) storing, (b) analyzing, and (c) displaying GIS data? (I humbly offer my reply to a related question ...