The information connecting numerical coordinates to actual locations on the earth.

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11
votes
2answers
729 views

Huge differences between results for 7-param datum transform

I'm trying to transform a WGS84 lat/lon point 11d42'32.10629" E 5d12'56.75371" S in three different software packages (Proj4, GeoTrans and Leica GeoOffice) but I receive very big differences ...
2
votes
1answer
60 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
152 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 ...
0
votes
1answer
89 views

Transforming from PSA56 to NAD83 using ArcGIS Desktop?

I need to transform some data from PSA56 to NAD83. It doesn't have to be that rigorous as it's purely for a context map. I'm guessing I will need to go to WGS84 and then to NAD83. If anyone has any ...
5
votes
1answer
116 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 ...
1
vote
1answer
547 views

How do you convert from GPS data in WGS84 to a GIS built in NAD27 in ArcGIS?

I have GPS data that has been recorded in Datum WGS84. The client has a GIS built in Datum NAD27. Having looked into the conversions online I would like to know how to do this rigorously with ...
3
votes
2answers
448 views

GeometryServer > Project with Datum Transformation

I am facing the problem that when i use the extent in the url and i go from Amersfoort(WKID 4289) to WGS84(WKID 4326) that without the tranformation the point from longitude and latitude is placed ...
2
votes
2answers
740 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 ...
2
votes
1answer
595 views

OpenLayers and custom Proj4 Projection

I am trying to map some planetary data on my webMap server using OpenLayers. I defined a proj4 projection as follow: Proj4js.defs["MYDATUM"] = "+proj=longlat +a=1740000 +b=1740000 +units=m +no_defs"; ...
1
vote
1answer
2k views

How to adjust online basemap to Arcmap

How can I adjust the online basemap imagery file to our existing ArcMap data. Below are steps I perform to add the basemap data. I Added basemap from "Add Data From GIS Online" in the file menu and ...
0
votes
0answers
269 views

How to find out what projection my data is using?

I have a set of data that I created from gps locations of images. The locations are in decimal. I don't know what projection was used when the data was captured. I used QGIS to display the data with a ...
1
vote
1answer
78 views

looking for datum to georeference maps of 19th century Maine

I am trying to georeference 3 (1840, 1844, and 1877) northern Maine maps. I really am not able to find which datum to use. Can anyone point me to a list of historic and regional datums? thanks
1
vote
1answer
46 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
0answers
694 views

How to set GDAL/cs2cs/proj to use NTv2 grid shift file when using EPSG codes?

I am using the GDAL API for Python for a script that takes only EPSG codes for inputs to specify source and target coordinate systems. While the cs2cs command seems to handle quite well ...
1
vote
2answers
420 views

define a datum and meridian in a CRS in QGIS

I have a shapefile defined by the source as: "The layer is in geographical (lat-long) coordinates (GCS_Clarke_1866; Datum: D_Clarke_1866; Prime Meridian: 0)." opening the shapefile in QGIS 1.8 the ...
9
votes
2answers
413 views

How do I perform a 3 parameter geotransformation and projection in Sql Server 2012?

I have a table with latitude longitude (NAD27) columns in it. I compute two other columns, X and Y, representing Web Mercator (WGS84) location. Currently I'm using a Arcmap to do this, by applying ...
3
votes
2answers
2k 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
197 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 ...
4
votes
1answer
294 views

Error in Min. Bounding Geometry results

I'm getting consistent, weird results from using Minimum Bounding Geometry to make circle polygons. I'm not sure if a datum issue, but I'm leaning more towards something wrong with Minimum Bounding ...
3
votes
1answer
2k views

ArcGIS 10.0/10.1 - arcpy - automate projection tool with different datum or projection

I am getting stuck with a task that is slightly different from the posts I found so far on this same website. Assumption: all layers have a defined coordinate system Problem: I would like to ...
9
votes
1answer
5k views

How to reproject a raster file in QGIS with datum transformation?

I want to reproject a tiff raster file from projection A (ETRS89/UTM Zone 32) to projection B (DHDN/Gauss-Kruger zone 2). The two projections have a different datum so I have to use a datum ...
1
vote
2answers
4k views

What do I need to change to get scale bar units other than degrees?

Measurements done in QGIS on my project are done properly using whatever unit is set in: Settings > Options > Map Tools > Preferred measurements units but the scale bar decoration and scale bar in ...
1
vote
1answer
3k views

How to Project shapefile from NAD 1983 UTM Zone 12 to WGS 1984 UTM Zone 13N?

I have a question and I have a shapefile that is in NAD UTM Zone 12 and Datum is North American Datum of 1983. What I would liket to reprojection it to NAD 1983 UTM Zone 13N and change the Datum to ...
1
vote
0answers
550 views

Possible to do a datum shift using dotSpatial?

I was hoping to be able to use Reproject.ReprojectPoints to achieve a datum shift between lat/lon values in NAD27 and NAD83. I'm able to correctly reproject from NAD27 lat/lon to NAD27 UTM and from ...
2
votes
3answers
463 views

Datum transformations, do we use wgs84 as an intermediate common reference?

I was transforming some data the other day using the 7 param helmert transformation and it got me thinking. I have a set of transformation parameters, but these only describe the transformation from ...
11
votes
3answers
374 views

Does Earth's magnetic field affect any datum definition?

I had an interview last week. One very interesting question was "does earth's magnetic field affect any datum definition?" I was sure it does not for geocentric datums. But I thought maybe the ...
0
votes
0answers
110 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. ...
1
vote
1answer
149 views

Tool For Generating Formula for Projection

I am using Proj4Js for northing,easting to lat,long transformation. My Datum is "AGD84" and projection is "Transverse Mercator". While doing so I found that if I don't specify "+proj" parameter in ...
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 ...
1
vote
0answers
415 views

Conversion From Transverse Mercator To Longitude & Lattitude

I have to transform (7-parameters datum transformation) coordinates from northings & eastings to lattitude & longitude. Following are details of source coordinate system(i.e. northings & ...
25
votes
1answer
9k 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 ...
3
votes
1answer
2k views

How to perform datum transformation in ArcGIS server REST API exportmap

I have a ArcGIS server 10.0 mapcontext in one projection (swedish grid sweref99 TM) which uses its own datum, also named Sweref99 . When I use the REST API's map service export function I want to ...
9
votes
1answer
6k views

Characteristics of different methods to convert ECEF to LLA

I'm trying to convert ECEF (Earth Centered, Earth Fixed) coordinates, which are defined in X,Y,Z, centered at (0,0,0) to LLA (Latitude, Longitude, Altitude). There are a couple of methods I found on ...
1
vote
2answers
4k views

Converting from British National Grid (27700) to WGS84 (4326) to Web Mercator (102100)

I'm developing a web application that uses ArcGIS to display a map using JavaScript. We are holding all our data in MS SQL Server 2008 as Easting/Northing against the British National Grid. ...
1
vote
1answer
464 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.
7
votes
3answers
8k views

What datum (reference ellipsoid) does Google Earth use?

What datum (reference ellipsoid) does Google Earth[1] use? I can't seem to find where Google Earth tells explicitly what datum they use. I need some sort of valid link. [1] The default free version ...
2
votes
3answers
139 views

What Danish position format is this?

I have been given a list of locations within Denmark. Most of the are in decimal degrees. However, some of the positions are in different formats and I can't figure them out. Does anyone recognize ...
4
votes
2answers
868 views

Converting Geocentric to Geodetic

I am only looking for a confirmation of what I believe to be true. If my explaination or conclusion is not accurate I would appreciate it if the reason can be explained to me. Background ...
2
votes
3answers
3k views

What Geotransformation (NAD27 to WGS84) should I use for Gulf of Mexico?

I'm working with datasets that are spread out across the northern part of the Gulf of Mexico, stored in NAD 27. I've been told the polygons shown above were obtained from BOEMRE (formerly known as ...
3
votes
1answer
380 views

What is the DNSC08 Mean sea surface model ellipsoid based on?

Does anyone know what Danish Space centre DNSC08 mean sea surface model uses as the reference ellipsoid? there is no meta data on the web site: ...
3
votes
3answers
1k views

Vertical Datum Conversion Utilities

I have some data (points and rasters) that I would like to be able to convert to and from several vertical datums, including MLLW in coastal Florida. I would appreciate it if people could provide some ...
12
votes
1answer
628 views

How is a “conformal latitude” used in ellipsoidal stereographic projections?

At my work, I've been doing some maintenance on internal software that claims to implement a Stereographic projection whose formulas were copied from an old system a long time ago. From what I've ...
6
votes
1answer
1k views

Determine the UTM zone/hemisphere in a particular datum

I'm using GDAL to convert coordinates from one system (geographic or projected) to another. Assume I want to convert geographic coordinates (latitude and longitude) in the WGS84 datum, to UTM ...
6
votes
2answers
7k views

Basic proj4 conversion UTM grid -> longlat and back

I'm a GIS novice, and am struggling to understand how to drive proj4 to accomplish what seems like a simple thing. I've googled for a couple of days, but everything I find seems to presuppose quite ...
8
votes
1answer
748 views

WGS72 to NAD83- how to find correct transformation

I am trying to get this raster file to convert from WGS72 to NAD83, but ArcMap10 doesn't appear to have the correct transformation listed. Where can I find this transformation, and/or how do I import ...
3
votes
1answer
754 views

datum conflict when creating buffer in arcgis 10

A buffer I created successfully executed, but I received the following message: "WARNING 000632: Datum conflict between map and output." How can I fix this?
5
votes
2answers
4k views

How do I use GDAL to convert from an arbitrary projection/datum into Equirectangular/WGS84?

I've been trying to use GDAL to convert from an arbitrary projection/datum into Equirectangular (aka Plate Caree, aka Equidistant Cylindrical, aka Geographic, aka Lat/Long) with WGS84 datum. All of ...
48
votes
7answers
4k 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 ...
5
votes
2answers
743 views

Why are the coordinates transformed with proj.4 off compared to http://valdemar.kms.dk/trf/?

I am trying to transform from epsg:4326 (wgs84) to epsg:25832 (utm ETRS89) using Proj.4. I am comparing the results with results from http://valdemar.kms.dk/trf/ . it seems like the results ...
4
votes
3answers
3k views

Parameters for ED50 -> ETRS89/WGS84 seven-parameter transformation which are good for Denmark?

I am looking for parameters for a seven-parameter transformation (Rx, Ry, Rz, Tx, Ty, Tz, s) from ED50 UTM (zone 32U) to ETRS89 and/or WGS84. The best match I could find is here: ...