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26 votes
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Changing shapefiles from geographic (WGS84) to projected (EPSG:2263) coordinate system using QGIS

This answer has four sections: What you should do to solve the problem and what you should avoid An example to better illustrate why assigning CRS and reprojecting are not the same An analogy that ...
Babel's user avatar
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23 votes
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Is the Geometry(4326) an alias for Geography datatype?

tl;dr: No. But see the update at the end. GEOMETRY and GEOGRAPHY are different PostgreSQL TYPES; exposed as higher level (SQL), user-defined composite types to the psql environment, but implemented ...
geozelot's user avatar
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14 votes
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What is meant with EPSG:4326 projection

You've got a good grasp of it. EPSG 4326 (i.e. WGS 84) is not a projection. But if you don't associate a projection to this geographic coordinate system, and naively render the coordinates as x/y ...
alphabetasoup's user avatar
12 votes
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How does QGIS calculate distances when the data is not projected (WGS84)?

Have a look under the "Project Properties" dialog. QGIS will use the project's settings for ellipsoid when calculating distances in a degree based coordinate system. If you're not using OTF ...
ndawson's user avatar
  • 27.5k
11 votes

Converting resolution in degrees to resolution in meters

Easiest way is to convert the raster to a projected system, and get the cell size directly in meters. That not being possible, or desirable, you can still convert lat/lon values to metric values, but ...
Roberto Ribeiro's user avatar
11 votes

What are the map units that WGS84 uses?

Be careful as WGS84 is a bit ambiguous. Most of the time it mean EPSG: 4326 that is indeed in degrees (and the base of GPS position) but the name WGS84 could be used for other CRS with different unit ...
J.R's user avatar
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10 votes
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R: Return the UTM zone that a WGS84 point belongs to

Each UTM zone is 6 degrees wide, so you can get the zone number by looking at the longitude: floor((longitude + 180) / 6) + 1 This assumes that you have longitude within [-180.0, 180.0).
Mike T's user avatar
  • 42k
10 votes

How does a Spatial Reference System like WGS84 have an elipsoid and a geoid?

WGS84 is natively XYZ, like the International Terrestrial Reference Frames (ITRF), and you can use an ellipsoid model to convert to latitude, longitude, and ellipsoidal height. Ellipsoidal heights ...
mkennedy's user avatar
  • 18.9k
10 votes

Generating polygon representing rough 100km circle around latitude/longitude point using Python?

I think I've found a working solution, using the Python geog library: https://pypi.python.org/pypi/geog import numpy as np import json import geog import shapely.geometry p = shapely.geometry.Point([-...
Simon Willison's user avatar
10 votes

Garmin FIT Coordinate System

For the latitudes and longitudes, you can divide the numbers by 11930465 (2^32 / 360) to get values in decimal degrees. The values seem to be stored in a signed 32-bit integer range, to represent the ...
FSimardGIS's user avatar
  • 3,836
8 votes

Converting WGS84 to ECEF in Python?

Here is a test(seems both methods work with same precision): import math import pyproj coords = [ (37.4001100556, -79.1539111111, 208.38), (37.3996955278, -79.153841, 208.48), (37....
mrgloom's user avatar
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8 votes

Why does Pyproj fail converting lon lat alt to ECEF?

Probably because in lon, lat, alt = 49.74761271, -113.2179781, 0 a lat of -113.2179781 is outside the valid bounds of -90 to 90.
BradHards's user avatar
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8 votes
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Generating polygon representing rough 100km circle around latitude/longitude point using Python?

An alternative solution would be to create a local metric projection and create the buffer in that projection. https://shapely.readthedocs.io/en/stable/manual.html#other-transformations tells you how ...
bugmenot123's user avatar
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8 votes
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Why is the length of one degree in Turf 0.9988?

This seems to be the end result of an interesting conversion from radians to degrees. t.convertLength(Math.PI,"radians","degrees") 179.78993435469053 PI radians should be 180 degrees. Looking at the ...
Spacedman's user avatar
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8 votes
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QGIS 3.6.1 problems with CRS

Following on Ian Turton's comment... Prior to performing ANY geometry calculations or analysis on a layer(s), the layer(s) MUST be 1) projected to the desired CRS, and 2) that CRS must be the same for ...
Stu Smith's user avatar
  • 8,172
8 votes

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

Mean Highest High Water is a reference surface corresponding to the height of high tides, averaged over a certain period of time (usually 19 years, a value close to a Metonic Cycle and a Lunar Node ...
FSimardGIS's user avatar
  • 3,836
8 votes

Use ST_DWithin on WGS84 geometry data

The problem is that you are using ST_DWithin on GEOMETRY objects with coordinates in WGS84. Therefore, your function call is requesting all features within 500 degrees (i.e., everything on the planet)....
hgb's user avatar
  • 1,154
7 votes
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Where to get world-map images for use in webglearth

You may check http://vterrain.org/Imagery/WholeEarth/ for links to satellite imagery, or http://www.naturalearthdata.com/downloads/10m-raster-data/ for raster images. These images can be tweaked in ...
MapTiler's user avatar
  • 1,621
7 votes
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Why is my coordinate notation different?

I'm not really sure but maybe check if you meant EPSG 4326 instead of 3857.
W. Tom's user avatar
  • 668
7 votes

Which is the most accurate method of measuring distance?

Let me focus just on the question of the most accurate way to determine distances on the WGS84 ellipsoid. The accuracy of Vincenty's method is about 0.1 mm providing it converges. It fails to ...
cffk's user avatar
  • 3,241
7 votes
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Geotools: unexpected difference between CRS.decode("EPSG:4326") and DefaultGeographicCRS.WGS84

I stumbled over a common pitfall. for EPSG:4326 the coordinate order should be latitude, longitude the javdoc for DefaultGeographicCRS.WGS84 state that the coordinate order should be longitude ...
evod's user avatar
  • 323
7 votes
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Difference between X,Y and Latitude,Longitude or Meters

For coordinates captured using a GPS, or by any means, longitude is the X value and latitude is the Y value. These are for a geographic coordinate system and have units of degrees. Alternatively ...
PolyGeo's user avatar
  • 65k
7 votes

Reprojecting EPSG:3412 to EPSG:4326 using GDAL?

According to spatilreference.org, your proj4 string is not correct. -a_srs defines the projection but does not modify the coordinates, so your output vrt file is likely to be incorrect (based on a ...
radouxju's user avatar
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7 votes
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Convert ERA5 data to WGS84

I ended up reaching out to the Copernicus support team and it turns out that ERA5 data is already referenced in the horizontal (lat/lon) with respect to the WGS84 ellipse so there is no need to ...
red's user avatar
  • 171
6 votes
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Relation between Geoidal separation and antenna altitude in GGA sentence?

The geoidal separation just reports the height difference between the ellipsoidal surface and the geoid model's surface. Natively, GNSS calculates ellipsoidal height (height above ellipsoid surface) ...
mkennedy's user avatar
  • 18.9k
6 votes
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Is a Helmert transform necessary to convert between WGS84 and NAD83?

Short answer is yes. You need to convert from your coordinates' native reference frame to the NAD83 realization's reference frame, then possibly add an adjustment. In the case of NAD83(CSRS), which I ...
Rob Skelly's user avatar
  • 3,101
6 votes
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Is WGS 84 datum, coordinate reference system, or both?

Both. It's also a geographic coordinate reference system and an ellipsoid, and sometimes a spheroid, and a bunch of other related/similar terms that are used in the fields of geodesy, geomatics, ...
mkennedy's user avatar
  • 18.9k
6 votes
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Guessing unknown projection in Malaysia

Malaysia uses Cassini projections per state for cadastral mapping. For Kuala Lumpur, the Selangor grid would be the right one. The EPSG registry lists these codes: 3380 GDM2000 / Selangor Grid 4393 ...
AndreJ's user avatar
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6 votes
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Issue converting projected coordinates to wgs1984 in Postgis

The spatial_ref_sys entry that spatialreference.org gave you was incomplete. It did not include the data to do the transformation from the Campo Inchauspe GCS to WGS84. Here's an entry that includes ...
Paul Ramsey's user avatar
  • 19.8k
6 votes

Which is the most accurate method of measuring distance?

For the sphere you can use the SLC (Spherical Law of Cosines). The HF (Haversine Formula) will work for this as well. You can use both of these on the ellipsoid and errors are typically very low (< ...
If you do not know- just GIS's user avatar

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