Questions tagged [datum]

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

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26 views

What are the standard values of the GPSMAPDATUM attribute in the exif standard?

I'm working on an application to read the exif georeferenced metadata of some photos. I would like to know all the possible values of the attribute GPSMapDAtum. Do you know where to find a list with ...
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2answers
63 views

Transform datum CSV->CSV using ogr2ogr

First I have a set of points in UTM 48S / WGS84 (EPSG 32748) as test.csv: X,Y,Z 9231824.04,787648.04,711.1442 Second I defined a test.vrt for ogr2ogr to read the data as follows <...
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1answer
24 views

Why are there differences in output position between the ArcGIS versus NCAT transformation [NAD83 to NAD83 HARN]?

My question is specifically referencing the file-based grid transformation methods that are now available in ArcGIS. I thought this grid-file method was exactly the same method that NGS's NCAT used ...
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27 views

How do you decide a new datum?

How do you decide datum size (axies a & b) and datum position relative to WGS84 (dx,dy,dz,rx,ry,rz) for a country if you were to create a new datum best fit for the country? Example, is datum ...
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1answer
33 views

NADCON 5.0 Transformations in ArcGIS

Are the new(ish) NADCON 5.0 transformations available in ArcGIS? If so, at what versions? If not, can they be added? Specifically, I am looking to go from NAD83(2011) to NAD27. I am ...
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1answer
23 views

Dynamic Text Datum properties in ArcMap

Is there a way to add the datum information to a layout using dynamic text in ArcMap. I am aware that the properties of the CRS can be added, including the datum name using but I am looking for the ...
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1answer
45 views

Convert IGLD85 to CGVD28 - Vertical Datums

I have water level data for the Toronto Harbour that states, "74.200 metres above IGLD 1985" I also have land elevation data around Toronto that uses the Geodetic Vertical Datum of 1928 (CGVD28) To ...
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1answer
51 views

Can we say ECEF datum like in Geodetic datum?

Commonly we use geodetic datum to describe the geoid, a distorted ellipsoid model of the Earth, but is it correct to say Earth-Centered Earth-Fixed (ECEF) datum? Because we are applying ECEF to a ...
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1answer
27 views

Transforming to GPS coordinates using projections with osgeo with Python

I am trying to transform a shapefile and its datum to GPS (EPSG Projection 4326 - WGS 84) but I get very different result on Google Earth, I write: from osgeo import ogr, osr file_name = 'POIS.shp' ...
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1answer
47 views

Create custom coordinate system

I have the following info from a data provider and need to create a custom coordinate system using these parameters. The end goals is to map a file in this coordinate system against other data sources ...
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1answer
49 views

What datums were used in North America before NAD27?

What datums were used in North America before NAD27? I googled around on this without luck. Also I found an old nautical chart of Lake Michigan, dated 1876, which states: Longitudes on this map ...
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23 views

Correlation between varying bearings

Problem: The Bearing of point B from point A on one datum and projection varies from that on another datum and projection. Can a consistent correlation be established for the variation in the Bearings?...
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46 views

ntv2 datum transformations-problem on file output

I am working with qgis 2.18.27 I have installed ntv2 datum transformations and it worked fine, but yesterday it didn't work and i am not finding the way to resolve the issue (explained below) I am ...
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1answer
139 views

How to apply a default datum transformation in an expression in QGIS

I'm using the expression: x(transform($geometry, 'EPSG:32632', 'EPSG:3003')) to add coordinates fields according to different CRS in a point layer. To obtain better accuracy i need to apply a Datum ...
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1answer
205 views

Translating WGS 84 datum to mean sea level?

I'm very new to GIS so here my question is I have WGS84 DEM data for my country and I want to calculate the sea level rise. I will use QGIS raster calculator, my problem is I need to find sea level ...
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1answer
69 views

Using NAVD88 geoid in Northern Canada?

The USGS NED (1-arcsec) dataset is available for the continental US as well as most of Canada. It is based on the NAVD88 vertical datum. I am interested in using the DEM to orthorectify SAR scenes in ...
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37 views

Sentinel 1 (A and B) Vertical Datum

I have been working through the ASF's "Recipes" for the creation of a DSM from Sentinel 1 (A and B) imagery. I am able to produce a DSM, and am relatively happy with the results in terms of the ...
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2k views

What Datum is used by Google Maps?

I am trying to convert vector shapefiles into Google Maps Datum using QGIS. Do you know which one is the datum? When I tried to convert them into WGS84 EPSG 3857, I could see that the shapes of ...
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109 views

NAD83 to NAD83(CSRS) transformation for Northwest Territories, Canada

I am looking to determine the correct Grid Shift Binary (gsb) file for transforming data from the NAD83 original to NAD83(CSRS) geodetic datum for the NWT in Canada. I was able to find reference for a ...
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1answer
148 views

What is the formula to convert geodetic coordinates to state plane?

I know there are tools that can do the conversion like pyproj, but I'm actually interested in the formula for computing it. Or if it's done with a big lookup table. I would love some information on ...
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2answers
599 views

Defining Latitude and Longitude before defining Datum?

Reference material: The Five Key Ingredients for Mapping the Earth There are five important steps to producing a map of the Earth's Surface. These are: sphere with north and south through the ...
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1answer
242 views

Datum transformation in QGIS 3

I have an Esri shapefile with following in the .prj file (broken into multiple lines for comprehension): PROJCS[ "SGL_Stereo", GEOGCS[ "GCS_SGL_GEO", DATUM[ "D_SGL", SPHEROID["...
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1answer
166 views

Pix4D and ODM generated tiff with same source images not aligning?

I have created two georeferenced orthomosaics using dronemade images. I used OpenDroneMap and Pix4D for that and I used the same source images for both. I thought that if I used the same images, the ...
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209 views

How to change the vertical datum of a geotiff DEM

I am trying to do some change detection between SFM derived DEM products, but the DEM i would like to use as my base elevation (and one other) is in NAD83, the remainder are WGS84. I would like to ...
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60 views

Missing datum only have lat long

I have some lat long coordinates but do not have any other information (datum, CRS etc) . I know where the place on Earth is but I cannot locate it (is a few miles off) using the coordinate numbers I ...
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1answer
176 views

Trimble 7X GNSS point Z returns negative elevations

I have a newly acquired Trimble 7X (with a centimeter kit). I collected a point in an area with a clear view of the sky. The accuracy indicator showed 1" accuracy and post processing and a ...
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1answer
59 views

Universal Datum Transformations between Rasters in ArcPy

Problem: Translating a set of various rasters with different datum into the same datum using ArcPy My Solution: Run rasters through a for loop, check their datum with an 'if' statement, run rasters ...
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1answer
155 views

Cannot assign custom projection to raster file in QGIS

I have a LiDAR data tile (raster file in GeoTIFF format) that is currently in WGS 84 (lat/long) geographic coordinate system. However, the data was collected in New Arc 1950 / UTM Zone 36 South ...
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2answers
76 views

Transforming Datum in Lat/Long to Projection in Feet

I am having issues projecting my csv file I have imported in lat/long to our state government-standard projection (EPSG 102121 NAD 1983 Michigan GeoRef (feet)), which is based on Oblique Mercator. ...
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2answers
523 views

Raster DEM vertical units are defined in meters, yet Arcmap displays them in feet

Background: I have received a single-band, 32-bit floating-point tif raster DEM, derived from a lidar project. The tif's XY coordinate system linear units are feet. Its vertical coordinate system ...
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1answer
343 views

How to map using more 'accurate' DATUM than WGS84? [closed]

WGS 84 is not very accurate as it is a compromise for the whole earth. Assuming theoretically I'm surveying using very accurate IMU and very accurate GPS (in WGS 84 of course). I think I'll get a ...
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2answers
770 views

Converting vertical datum from WGS84 to EGM96 in ArcGIS Desktop?

I am comparing two different Digital Elevation Models SRTM (Datum: EGM96) Cartosat (Datum: WGS84) How to convert WGS84 to EGM96 in ArcGIS Desktop?
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1answer
46 views

Is it acceptable to assume there will be no 'walk' in coordinates transformed back and forth between two datums?

Given that you use the same datum transformation, you should end up with the same coordinate regardless of how many times you convert between to datums. Is this a correct assumption? Is this ...
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0answers
191 views

Postgis st_transform precision

I am checking effects of reprojecting planar coordinates from one CRS to another and back, keeping the same DATUM, and I was trying to determine the cause of the loss of precision. I know that ...
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1answer
426 views

Transforming from NGVD29 to EGM96/WGS84?

I have this USGS reservoir elevation in NGVD29 datum and I want to transform it to WGS84 ellipsoid (SRTM 1 ArcSec DEM). How can I transform this point data (NGVD29) to EGM 96 or WGS84 ellipsoid so ...
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2answers
67 views

Trying to project a shapefile to line up with another shapefile?

I have two polygon shapefiles representing district boundaries: Districts1 and Districts2. They are supposed to represent the same geographical area and same district boundaries, but I realized that ...
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1answer
27 views

What (where) are elements that comprise WGS60 and FSHR1960?

Considering two 1960 geodetic ellipsoids (from this list), I've found the following parameters (from here): WGS60: World Geodetic System of 1960: 6378165.0, 298.3 FSHR1960: Fischer – 1960 (Mercury):...
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1answer
76 views

Calculating Datum Corrections to Overlay pre-NAD27 USGS Maps?

I am working with some older (ca. 1900) USGS Topographic Maps. These Raster maps are georeferenced with a CRS of NAD27 and poly projection (polyconic). However, they are offset and require easting/...
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2answers
2k views

Convert Geoid File Types

Anyone know what I can use to convert a geoid surface stored as , BYN into .GTX for use with PROJ4? The CCG2013A vertical datum and geoid model from NRCan is only available, as far as I can find, in ...
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1answer
70 views

What vertical datum for OpenDroneMap with no GCP

I am processing drone imagery with OpenDroneMap using a native Ubuntu installation of OpenDroneMap. I see the the LAS generated returns points in UTM for X and Y coordinates as stated in the ...
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1answer
214 views

NOAA vdatum GDAL Variable Paths for Linux Ubuntu

I want to do vertical datum conversions on geotiffs using NOAA vdatum The conversion status menu shows no progress and no conversion happens. I see that Microsoft Windows needs GDAL environmental ...
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1answer
399 views

Determining Layer's DATUM and PROJECTION in “Layer Properties” (QGIS)

I have two layers in a QGIS project: "Layer 1" and "Layer 2". In their "Layer Properties" under "Coordinate Reference System" I see this: Layer 1 Layer 2 I'm trying to understand the differences ...
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1answer
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Unable to transform feature classes having GCS_WGS_1984 to the current data frame layer (NAD_1983_UTM_Zone_10N)

This is my first time posting here, so I apologize if my question seems too basic. I am designing a map of various locations that are of interest to my organization. I've obtained all of the layers ...
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0answers
222 views

Spatial reference conflict: WGS84 or clrk66

For a raster dataset, trying my.raster@crs or proj4string(my.raster) in R gives the PROJ.4 string "+proj=longlat +ellps=clrk66 +no_defs". I downloaded the raster from SEDAC here - the World link, ...
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1answer
708 views

Convert NGVD 1929 to NAVD 1988?

My root issue is that I have elevation values in NGVD 1929 that need to be related to a DEM which has elevation values in NAVD 1988. Is there a way that I can convert elevation from one data to ...
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0answers
500 views

What's the difference between NAD83(2011) (OGR WKID 6318) and GCS_NAD_1983_2011 (ESRI WKID 6318)?

I just projected a feature class originally in Web Mercator (WKID 3857) to WKID 6318 (ESRI calls this "GCS_NAD_1983_2011") using ESRI's projection tool, and the same feature class to WKID 6318 (OGR ...
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1k views

What WGS84 epoch date is used by Google Maps

I have some Nad83 data that I want to overlay on Google Maps. This article by ngs.noaa.gov explains translating from nad83 to wgs84 better than anything I have read. If I were to use a tool like the ...
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2answers
578 views

Project data between different datums using custom parameters in QGIS!

I want to convert or reproject in the fly some shape files and raster between between different datums using custom transformation parameters (7 parameters) but don't know how to do that in QGIS. I ...
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0answers
205 views

Get Transformation method and Parameters from coordinate system

I have data (vectors, and raster) that are in UTM coordinate system, and I need to reproject them to a local coordinate system. Unfortunately, I do not know the transformation method that I may use ...
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2answers
1k views

Why does WGS84 refer to so many different things?

Sounds like a stupid question, but I've been struggling with this. Here's a diagram of the structure for EPSG 4326 - the geographic CRS known as WGS 84. Here we have WGS 84 (a CRS), World ...