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Questions tagged [ellipsoid]

An ellipsoid is a closed quadric surface that is a three-dimensional analogue of an ellipse. In geodesy, a reference ellipsoid is a mathematically-defined surface that approximates the geoid, the truer figure of the Earth, or other planetary body.

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Finding the right Projection/CRS for a 2000's era shapefile of Bosnia Herzegovina

I have been looking for a historic soil map shapefile of Bosnia & Herzegovina for a while and finally found one - a UN FAO project archive had the files available, albeit designed for ArcView. The ...
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Intersect a 'circular' sector with a 'square' on WGS84

I wold like to get the intersection(if empty or not) and area of a circular sector defined by the origin(lat, lon), bearing and angle width with a 'square' defined by lines of constant lat and lon on ...
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Making transformations between ellipsoids using PyPROJ

I am transforming coordinates between the Ellipsoids WGS84 and Hayford International using the code from pyproj import CRS, Transformer Define CRS objects for WGS84 and Hayford International ...
nic's user avatar
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Reprojecting image with ground control points in geodetic CRS to equidistant cylindrical CRS on sphere

I'm working with some satellite data from the Mars Reconnaissance Orbiter context camera (CTX). As a sanity check for some later processing that I would like to do, I'm trying to take the raster data ...
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QGIS ellipsoidal area values changing very slightly between calculations while planimetric values stay the same

I have a number of vector shapefiles that I need to calculate the geodesic/ellipsoidal area for. These shapefiles are accessed and updated regularly, with the area recalculated each time they are ...
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How can Cartesian and ellipsoidal perimeters and areas be so different in an EPSG:3857 layer?

For a particular polygon of mine in a "EPSG:3857 - WGS 84 / Pseudo-Mercator" layer, the derived measurements QGIS reports are: Ellipsoidal perimeter: 1015 m Cartesian perimeter: 1218 m ...
Geremia's user avatar
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Projection alignment

I am trying to align my coordinates with known geodesic markers in QGIS 3.34.1 but all my measured points are out with a bearing of about 35 degrees and 2.6m away. My distances are correct when ...
Stephen's user avatar
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QGIS measurement tool seems unrealistic

I have created a buffer of 150m around a point. This should give (a polygonal approximation of) a circle with radius 150m. I tried to verify this with the measurement tool, and I am baffled to see a ...
AEF's user avatar
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Create one-sided-ellipsoid from 'geometry by expression'

I am looking for a way in which, I can create a buffer around a point. The buffer is meant to be a semi-ellipsoid. In theory it should be a mixture of 'single_sided_buffer' and 'make_ellipse' ...
Berit_GFA's user avatar
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Coordinate reference system for wide areas in Canada

I am using imagery from different sensors (Sentinel 2 and high resolution satellite) in several areas in Canada. I am trying to accurately represent areas (polygons), however when merging information ...
Marlon Calispa's user avatar
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Convert XYZ file with WGS84 Ellipsoid elevations to EGM96 Geoid elevations

I have multiple files in XYZ format in UTM horizontal + WGS84 ellipsoid vertical that I need to convert to UTM horizontal EGM96 geoid elevations. There are about 250'000 points in a an area that is ...
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How to calculate the curvature of a segment of an ellipsoid

I'm an artist trying to sculpt shapes that I would describe as ellipsoids. I am wanting to sew together fabric to form these shapes, and although I know the dimensions of the ellipsoid I want to form, ...
kris's user avatar
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4 votes
2 answers
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How to convert wgs84 from ellipsoidal height to mean sea level i.e. height above goid, with pyproj?

I want to convert wgs84 coordinates with ellipsoidal height to wgs84 coordinates with height above goid. Therefore I have set up a new conda environment and installed pyproj, proj_data, see conda list ...
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Measuring distance using QGIS

Normally if you measure the distance of line and polygon in Cartesian is smaller compare to Ellipsoidal in QGIS. However, when I am measuring the distance Cartesian system gives greater value compare ...
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Error in WGS84 to Mercator coordinate transformation

I'm trying to convert the (lat,lon) of WGS84 into Mercator (x,y). Below I've listed all the relevant information given in the file. Datum="WGS84" Ellipsoid="WGS84" ...
Pixel_Bear's user avatar
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3 answers
3k views

Is EGM2008 different to WGS84 ellipsoid?

I have a DEM dataset which describes the vertical reference used as "height above the WGS84 ellipsoid". As I understand it this assumes vertical values to have MSL as a reference and NOT ...
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Interchangeability between ellipsoidal CRS, and spherical CRS with the authalic radius of the same ellipsoid?

The Uber H3 documentation states: The coordinate reference system (CRS) is spherical coordinates with the WGS84/EPSG:4326 authalic radius. It is common to use WGS84 CRS data with the H3 library. To ...
shadowtalker's user avatar
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150 views

How to check Length calculated in Cartesian or ellipsoid?

I am trying to do offset curve of a line my layer projection is ESPG:3857 WGS-84\pseudo-Mercator lyr=iface.activeLayer() geom=lyr.selectedFeatures()[0].geometry() newgom=geom.offsetCurve(5,2,1,0.0001) ...
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3 votes
1 answer
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Finding correct ellipsoid to calculate the surface of polygons (hectares) in QGIS

I would like to calculate the surface of a group of polygons in QGIS. It was not me to create the shapefile, when I add it to the project and I check its properties, it results that the geometry and ...
Geo_it's user avatar
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2 votes
1 answer
534 views

Adding EPSG:7019 (GRS 1980) to PostGIS

I have been trying to add the ESPG:7019 to my postGIS DB using INSERT into spatial_ref_sys (srid, auth_name, auth_srid, proj4text, srtext). I am trying to find the right definition to use inside this ...
rm167's user avatar
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9 votes
2 answers
592 views

Creating ellipse around line in 3D space using R

BACKGROUND: A similar question has been asked before, but not answered; see Creating ellipse around line in 3D space using PostGIS. I am a new user asking this question but hopefully with more details....
Wu Wei's user avatar
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What are elipsoid parameters of SoilGrids?

For point sampling in R I need information of the underlying ellipsoid parameters of the database Soilgrids, because they seem to be different from other layers I am using. I couldn't find any ...
Niklas Bosch's user avatar
2 votes
1 answer
189 views

OGRSpatialReference works with proj4 string in GDAL 2 but not GDAL 3

I have the following proj string: +pm=greenwich +ellps=GRS80 +a=6.37814e+06 +rf=298.257 +proj=tmerc +units=m +to_meter=1 +lat_0=42.5 +x_0=500000 +y_0=0 +lon_0=-72.5 +k_0=0.999964 +vunits=m and I have ...
Marcus Elia's user avatar
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1 answer
962 views

Calculate orthometric height with geoid ITRF97 and ellipsoid WGS84

I'm trying to calculate the orthometric height between ITRF97(or EGM96) and wgs84 (or grs80) in specific latitudes and longitudes. For example: in longitude 57.111 and latitude -5.582 i used an online ...
I d's user avatar
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3 votes
1 answer
3k views

Getting accurate distance measurements using EPSG:3857 in QGIS

I'm still a beginner at QGIS and am currently using it to plan trap placement for an upcoming fieldwork session in Central Europe. Traps should be placed along a transect 100m apart. So far when I ...
Yzma13's user avatar
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3 votes
0 answers
184 views

How does grass r.viewshed take into account the Earth curvature?

Up to now I always had to do such analysis in a local Cartesian Coordinate System and on relatively small datasets, but today, I want to compute a viewshed analysis on a large raster DEM which is ...
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Performing ellipsoid to spheroid conversion using ArcMap

I have a DTM that is referenced to an ellipsoid (equatorial radius is not equal to the polar radius) and I want to convert the elevation values to the spheroid (equatorial radius = polar radius). How ...
Ranjan's user avatar
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0 answers
286 views

Resizing objects from Cartesian measurements to Ellipsoidal

I have been working on a project in QGIS 3.12.2 in EPSG 3857 so it works with google earth. Without realising the difference there would be between cartesian and ellipsoidal I buffered some points. By ...
TL95's user avatar
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2 votes
1 answer
778 views

CRS for Ellipsoid Measurements

I noticed within the "Project Properties" there's an option for, Measurements --> Ellipsoid. What should this setting be configured to? From what I read online, if this is set incorrectly,...
Sir.Socks's user avatar
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4 votes
1 answer
947 views

Cesium OSM buildings floating in the air; could we set a custom ellipsoid, locally more accurate?

I just discovered the way to include OSM building data in a Cesium project. It sounds great but I also (re)-discovered my local ellipsoid vertical offset with the global WGS84 one (see pictures). The ...
swiss_knight's user avatar
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5 votes
1 answer
255 views

Changing the method of the area command from planimetric to ellipsoid in QGIS

I am trying to use the QGIS Field Calculator to calculate the area of a feature. When I do this, the area returned is calculated using the planimetric method. This differs to $area which uses the ...
hojkoff's user avatar
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5 votes
1 answer
494 views

Measuring distances on custom ellipsoid

I'm trying to set up a QGIS project for creating a map of a fictional planet smaller than Earth. See here for a helpful question that doesn't quite touch on what I'm trying to accomplish (I don't mind ...
Coel's user avatar
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0 votes
1 answer
430 views

How to extract CRS ellipsiod info in correct format for pyproj inverse

I am using pyproj inverse transform to add azimuth and distance "info" to an ordered geodataframe (gdf), but my datasets are in different locations around the world. I need to use a local ...
a11's user avatar
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2 votes
1 answer
250 views

PyQGIS - get ellipsoid acronym of coordinate system of layer

I want to calculate the area of polygons in a layer with PyQGIS. I am using the following code: d= QgsDistanceArea() for feature in layer.getFeatures(): area = d.measureArea(feature.geometry(...
Marshal Mappers's user avatar
7 votes
1 answer
628 views

What is MHHW Mean Highest High Water, in terms of datums/coordinate systems?

I'm modeling sea level rise, which entails adding the projected sea level rise for a specific decade to the current MHHW height (I think. I am new to this.) My question is very general--what is MHHW ...
Jeff's user avatar
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1 vote
0 answers
227 views

QGIS DXF measurements in AutoCAD are in Cartesian and not Ellipsoidal

I'm trying to export some land boundary polygons to AutoCAD using the Export to DXF function. The issue I am having is that the distance measurements in AutoCAD, of the exported DXF file, represent ...
Yazki's user avatar
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1 vote
0 answers
323 views

Convert ellipsoid height to geoid using SpatiaLite

I would like to convert ellipsoid height to geoid (EGM2008) using SpatiaLite. is there any query that we could achieve this?
Mani devs's user avatar
1 vote
1 answer
253 views

QGIS 3.10 Populate attribute table with ellipsoidal distances along lines

I have a GIS with a logistics layer that contains line features. The lines have been digitised from aerial photography and each line represents a path from A to B, following roads, rail and waterways. ...
Sangster's user avatar
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7 votes
3 answers
1k views

Calculating elipsoidal length of line in PyQGIS

I am using PyQGIS with QGIS 3. This code below is what I developed already, what I am doing wrong? layer = iface.activeLayer() feature = layer.getFeatures() for feat in feature: feature....
vitorcsm's user avatar
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0 answers
384 views

Convert heights from DHDN Gauß Krüger Zone 4 to UTM 32 ETRS 89 in pyproj

I am using pyproj. X/Y conversion is pretty straightforward through transformer = Transformer.from_crs(31468, 25832,always_xy=True) However, this does not transform the heights. From Vertical ...
Terranigmus's user avatar
2 votes
1 answer
880 views

QGIS Buffer distance vs Distance in Distance Matrix

I created Buffer (with Vector, Geoprocessing Tools) with 500 M distance from a point in the map (let's say Point A). I made another point (Point B) and it is not inside the 500 m Buffer. The Distance ...
necrohiero's user avatar
1 vote
1 answer
2k views

How to set global setting ellipsoid in QGIS?

Is it possible to define ellipsoid (None/Planimetric) into QGIS environment, not only for Project environment? I use calculations without ellipsoid, but sometimes I forget to make ellipsoid as None/...
GISU's user avatar
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3 votes
1 answer
547 views

Gravity related height from ellipsoidal height using pyproj

I'm using the pyproj library (http://pyproj4.github.io/pyproj/stable/index.html) to get translate ellipsoidal heights into gravity related height. Code: from pyproj import CRS from pyproj import ...
Jonas Paludan's user avatar
4 votes
1 answer
779 views

QGIS 3.6.1 problems with CRS

After I have created a new QGIS project, the project CRS is set automatically to WGS84 (EPSG:4326 - WGS 84 - Geographic). The layer (.shp) which I loaded to the project has already a predefined CRS (...
Mapos's user avatar
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3 votes
2 answers
188 views

Ignoring ellipsoidal heights recorded from GPS when only interested in location?

I am not interested in converting ellipsoidal height into AHD heights, because I have a good DEM. However, this whole business about geocentric vs geodesic coordinate systems is thoroughly confusing ...
Visithuru's user avatar
3 votes
2 answers
3k views

Calculating geodesic distance along a path (lat/lon points) at once?

Using Python 3.7 with Jupyter Notebook on a Win10 x64. I have a list of lat-long tuples representing a path and I want to calculate the total length along that path in meters (or km, miles etc). I ...
VictorX's user avatar
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6 votes
1 answer
2k views

Correct area calculations: When to use planimetric, when ellipsoidal?

Sometimes I am not sure whether to use planimetric or ellipsoidal model to calculate areas of polygons. If there is a "reference" data (e.g. a given shape_area column) I compare results and take the ...
user16032's user avatar
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2 votes
0 answers
548 views

Stereographic projection of WGS84 ellipsoid [closed]

According to this source, an optimal projection for small, roughly square areas is the stereographic projection. The wikipedia page of the stereographic projection shows how to convert from spherical ...
Ricardo's user avatar
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1 vote
0 answers
537 views

Underlying distribution of points in an ellipse

I'm attempting to generate both a uniform distribution and a normal distribution of points that fall within an ellipse shape, made from a centre point, semi major and minor and rotation in degrees. I ...
saph_top's user avatar
  • 284
1 vote
1 answer
274 views

Bessel ellipsoid definition for LV95 (EPSG:2056)

I recently wrote some code to transform coordinates between WGS 84 and the new Swiss projected coordinate system (LV95 / EPSG:2056). While doing that, I tried to find an authoritative source for the ...
ValarDohaeris-fuck-OpenAI's user avatar