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

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3
votes
1answer
649 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"; ...
173
votes
11answers
61k views
8
votes
1answer
162 views

What is my coordinate system preserving?

I'm trying to get a better grasp of coordinate systems, datums, projections etc. I understand that certain systems preserve different things; distance, shape, angles, area. I'm wondering how you can ...
0
votes
0answers
29 views

Algorithm for converting from projected coordinate system to geographic one using Helmert transformation

I have a data in projected coordinates system and I need to convert them to WGS84. I know the parameters of position vector transformation and I know the projection details of my projected coordinate ...
3
votes
1answer
40 views

VDatum helmert transform parameters

I'm trying to use NOAA's VDatum to verify the NAVD88 -> WGS84 datum conversion in a c++ datum conversion library that I've written. The answers didn't agree, so I attempted to check a simple ITRF2008 ...
1
vote
0answers
33 views

6 degree of freedom helmert transformation

I'm looking to do datum conversions for points with six degrees of freedom, that is, they are described by a heading, pitch, and roll in addition to their position information. I know how to convert ...
0
votes
0answers
37 views

gdaltransform returns ERROR 1: failed to load datum shift file

I'm trying to do a NAVD88 to WGS84 (G1674) conversion using gdal. I've installed gdal (on centos7) using sudo yum install gdal proj-epsg proj-nad and am trying to perform the conversion via: ...
1
vote
0answers
25 views

QGIS x ArcGIS - Geoprocessing Vectors in Geographic Coordinate Systems [closed]

Is there a possibility of in future versions of QGIS, the software be able to geoprocess vectors (clip, buffer, intersection, etc.) in Geographic Coordinate System, and not only in UTM? In ArcGIS, ...
1
vote
2answers
81 views

Datum shift issue between OSGB1936 and WGS84

I have to work between OSGB1936 and WGS84 and BOTH of these data sets started out life as OSBG1936 BounaryLine data. I thought I was just at the end of a full revision of my master mapping until I ...
1
vote
2answers
152 views

Is WGS 84 datum, coordinate reference system, or both?

The background to this question is in Understanding difference between Coordinate System and Projection? There @mdsumner commented: WGS84 is not a cs, it's a datum. On a couple of places online ...
3
votes
3answers
3k views

What Geotransformation (NAD27 to WGS84) to 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 ...
1
vote
1answer
887 views

What is/are the coordinate systems used in South Africa?

What are the principal datums and projections used in South Africa including the names of geodetic datums and their projections?
3
votes
1answer
55 views

Why does QGIS do an unintended datum shift to WGS84 in the map canvas

I'm a new QGIS user running 2.12 Lyon. I've encountered an issue with map canvas units and an unexpected and transparent datum transformation to WGS84. I need help figuring out if I've missed ...
4
votes
1answer
81 views

Datum and transformation error using ST_Transform in PostGIS, going from NAD83 to NAD27

I created a function in PostgreSQL to transform input coordinates using UTM Zone 12/13, with Datums NAD83 or NAD27, to the WYLAM projection. I had to manually create the entry for the proj4text ...
4
votes
1answer
90 views

WRF Spherical Earth to WGS 84

Weather Research Forcasting Model assumes a spherical earth model with a radius of 6370km. I'm looking to display the data onto the WGS-84 Ellipsoid model as that is the model my system uses for its ...
11
votes
1answer
691 views

why does the North American Datum not actually include north america in it's boundary?

http://spatialreference.org/ref/epsg/4269/ That link shows the area that the North American Datum 1983 covers and one thing I note is that it doesn't cover North America. It covers all of Asia and ...
6
votes
3answers
136 views

Vertical datum query for coastal modeling

This may be very specific. I have a USGS derived DEM with a vertical datum of EGM96 from NASA satellite data. My Bathymetry uses a lowest astronomical tide datum. Has anybody come across this or ...
0
votes
1answer
36 views

How to set datum in GPS connection setup window in ArcFM Viewer for ArcGIS Engine Application

I have a custom application based on ArcFM Viewer for ArcGIS Engine. I want to use an external GPS receiver with that application and the setup window does not let me choose a different geographic ...
3
votes
2answers
76 views

How to re-project a shapefile to be compatible with another shapefile or raster?

I have a polygon shapefile and a raster. The shapefile and raster have different coordinate systems. Coordinate System for the shapefile: NAD_1983_UTM_Zone_19N WKID: 26919 Authority: EPSG ...
1
vote
0answers
64 views

Strategies and methods that Datums and Coordinate Systems use to account for movement of the earth's surface

Are there datums and coordinate systems that address the issue of shifting coordinates through time? If so, what are some of the strategies and methods that the datums and coordinate systems use to ...
3
votes
1answer
159 views

Difference between datum and ellipsoid for geodetic coordinates?

Looking at the Wikipedia page for the North American Datum, it seems to imply that the datum is completely defined by the ellipsoid, which defines the major/semi-major axes, flattening, etc. For ...
1
vote
0answers
44 views

Are ellipsoid and datum the same? [duplicate]

Are the datum and the ellipsoid the same? What is a Datum? The Earth is shaped like a flattened sphere. This shape is called an ellipsoid. A datum is a model of the earth that is used in mapping....
0
votes
0answers
24 views

Valid Range of Geoidal Separation in GNS and GGA sentences

I haven't seen any information about valid ranges of geoidal separation in GGA and GNS sentences. I am using Nema Studio Simulator to simulate GPS receiver. In there Geoidal Separation can be set to ...
1
vote
2answers
808 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 ...
2
votes
1answer
240 views

Relation between Geoidal separation and antenna altitude in GGA sentence?

I have searched about definitions and relations about geoidal separation and antenna altitude reported in GGA sentence. The more I read the more I am confused.So in a simple manner can anyone explain ...
3
votes
0answers
52 views

Do locations “move” when shifting datum?

I hope that this is the right Stack Exchange for this question. I may be oversimplifying this, but I'm looking for verification in my understanding of the following: If I have a spatial dataset in 2 ...
8
votes
3answers
9k 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 ...
4
votes
2answers
125 views

Are Australian Height Datum and GDA94 applicable to Christmas, Lord Howe, and Norfolk islands?

I've been asked to recommend a mapping coordinate reference frame for use for Australian mapping, which I've said AHD for the vertical component and GDA94 for the the horizontal component. However, I'...
0
votes
1answer
92 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 ...
4
votes
2answers
1k views

Geographic Transformations in Alaska Between NAD83 and WGS84

I have done a ton of research on the most accurate transformation to use in mainland Alaska to convert between the NAD83 and WGS84 datums, but I just can't seem to find a definitive answer. ArcMap ...
3
votes
1answer
49 views

What does it mean for two datums to be navigationally equivalent?

I read from NOAA that NAD83 and WGS84 are "navigationally equivalent" NOAA uses the North American Datum of 1983 (NAD 83) for all of its charts. This datum is navigationally equivalent to the ...
10
votes
3answers
1k views

What is the meaning of “Elevation above the surface of the ellipsoid”?

I'm using implementation of Vincenty's algorithms, and I have their class called "position" that requires lat, lon, and elevation defined by: "Elevation above the surface of the ellipsoid". What is ...
39
votes
2answers
5k 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 ...
3
votes
2answers
3k 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
3answers
1k views

Why does my map look stretched out?

I've decided to give this map design thing a go - I downloaded the USA counties shapefile from National Atlas, exported them to SQLite from QGIS, and then linked the SQLite file in Tilemill, and this ...
0
votes
1answer
195 views

Difference between WGS_1984_UTM_33N and GCS_WGS_84

What is the difference between: a map that has a projected coordinate system of WGS_1984_UTM_33N, a geographic coordinate system of GCS_WGS_1984, and a datum of D_WGS_1984 a map that has no ...
3
votes
2answers
295 views

methods for converting coordinate datum and format in python?

Related to an earlier Q&A of Missing grid shift files for cs2cs.exe? ... what are the various methods to convert coordinate datum and format in python? (Windows Vista, python 3.4) For example, ...
1
vote
1answer
92 views

Geosoft Oasis Montaj Local Datum Transform - What is the purpose of this parameter?

When defining a coordinate system in Oasis Montaj one of the parameters is "Local Datum Transform". Is this the coordinate transformation definition to convert the defined coordinate system of a data ...
3
votes
4answers
1k views

“Horizontal” and vertical datums terminology

I have heard people referring to as a horizontal datum to models such as WGS84 and as a vertical datum to geoids. The former is primarily used for determining latitude and longitude but also the ...
2
votes
2answers
5k views

Transforming coordinates between wgs84 and UTM ED50 31N, what am I missing?

My problem is I must tranform a point cloud from wgs84 (geographic) to UTM (projected) ED50 for zone 31North. Easy, isn't it? Well, first surprise is I have several free webs who offer me this ...
2
votes
1answer
211 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 ...
1
vote
2answers
5k 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
0answers
42 views

Geographic coordinate system and datum [duplicate]

I am bit confused about datums used to define a localised coordinate system for a specific area. Definitions say that, datum defines how a certain well-established point (i.e., reference point) on ...
0
votes
1answer
87 views

ArcGIS 10.2.2 Does “Batch Project” work for different input datum?

I have two vector data sets - one is in NAD27 and the other is in WGS84. Normally I reproject one at a time. But can I just use 'batch project' to reproject both of them to NAD83 at once? I was not ...
4
votes
1answer
557 views

Canadian Geodetic Vertical Datum of 2013 (CGVD2013)

"Natural Resources Canada (NRCan) has released the Canadian Geodetic Vertical Datum of 2013 (CGVD2013), which is now the new reference standard for heights across Canada. This new height reference ...
1
vote
1answer
301 views

Transform coordinates in MapInfo with GSB data

Does anybody know if MapInfo (or MapBasic) is capable to do coordinate transformation using the NTv2 (National Transformation version 2) method? Currently Switzerland changes their national ...
3
votes
1answer
234 views

Reprojecting between NAD27 and WGS 84 part III

I am trying to perform a reprojection for data with datum Nad27 to WGS84 datum. According to AndreJ in some previous questions in Stackexchange (CRS reprojection for instance) QGIS uses internally by ...
1
vote
1answer
3k 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
1answer
58 views

Converting datum?

I need to measure the distance (with the ruler) of points from two different layers. However, one layer is NAD83 and the other is NAD27. I also have a standard ESRI basemap downloaded. The issue I ...
1
vote
1answer
324 views

Project from Datum Nad27 to WGS84

This should be simple: have a shapefile in UTM z16 DatumNad27 and want to transform it to Datum WGS84 latlon I am using Qgis 2.6 Sorry I am going to clarify, with the steps taken: 1- XY data of a ...