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7 votes

Get lat/long given current point, distance and bearing

What follows is a development of the formulas found in the Aviation Formulary by Ed Williams and in Movable Type Scripts by Chris Veness, from the formulas of spherical trigonometry, to solve the ...
Gabriel De Luca's user avatar
6 votes
Accepted

QGIS Transformations with respect to desired epoch

Make sure you have QGIS compiled against a GDAL/OGR version greater than 3.4: We can perform the vector transformation with the Convert Format process (you can look it up in the Toolbox even as ...
Gabriel De Luca's user avatar
4 votes
Accepted

EPSG code for a 3D CRS based on WGS84?

EPSG/WKID number 4326 relates to WGS84 Geographic, with units in degrees. The ellipsoid is extremely similar to GRS80, with only a slight difference in one of the axes. This is the code and system ...
AlecZ's user avatar
  • 2,633
4 votes
Accepted

Planimetric Area Measurement in Geographic Projected Vector Data in QGIS3

You are computing ellipsoidal areas (using the $area geometry function in the expression). But changing the reference ellipsoid from WGS84 to a plane. If you use area($geometry) expression instead, ...
Gabriel De Luca's user avatar
3 votes
Accepted

Adding EPSG:7019 (GRS 1980) to PostGIS

GRS 1980 is defined by two measurements: Semi-major axis = 6378137 Inverse flattening = 298.257222101 With this, you've defined an ellipsoid, but you do not have a coordinate system. Where is Europe ...
Mintx's user avatar
  • 5,396
3 votes
Accepted

Online PPP Services?

You may also use APPS (https://pppx.gdgps.net/) It's a technology from NASA's Jet Propulsion Laboratory and they use there own GipsyX/RTGx software for processing the GPS measurements.
Germain Roussez's user avatar
3 votes

Local Cartesian (NED) to Geodetic (Lat,Lon,Alt) Conversion - Max Distance from Reference Point

I don't think there are practical limitations to ned2geodetic. The conversion from LLA to ECEF coordinates has closed form solution. The rotation of NED vector to ECEF has closed form solution. ...
Mario Chang's user avatar
3 votes

Moving dead ahead: rhumb line, great circle or none

I know the question has answered already, but allow me to show you something cool for future use: A live Google map where you can move the edge markers affecting the great circle and rhumb line same ...
hookie's user avatar
  • 31
2 votes

Which of EGM96 geoid or WGS84 ellipsoid fits the earth better?

The answer depends on what you are interested in and therefore what you mean by 'earth's surface'. The Geoid is the equipotential surface (in terms of gravitational potential). The ellipsoid is a ...
Sharad's user avatar
  • 109
2 votes
Accepted

Recommendation for a book for geographical distance calculations

One place to start is the bibliography provided by the geographiclib of Charles Karney. This starts at the begining with: I. Newton, Philosophiae Naturalis Principia Mathematica (3rd edition, ...
Ian Turton's user avatar
  • 82.2k
2 votes

Can't get RTKLIB to use an external geoid

You are missing the out_geoid option. My working file looks like: ... out-height =geodetic # (0:ellipsoidal,1:geodetic) out-geoid =egm96 #(0:internal,1:egm96,2:egm08_2.5,3:...
Dave X's user avatar
  • 1,699
2 votes

Do different ellipsoids have different location of centre?

If two ellipsoids share the same origin and axes (both use Greenwich and the same North pole), but have different axes lengths, only the geodetic latitude will change between the two. This is true ...
mkennedy's user avatar
  • 19k
2 votes

What's the name of the area between two geographic coordinates?

A quadrangle? Yes, it is named: spheroidal quadrangle.
Gabriel De Luca's user avatar
1 vote
Accepted

What does "spherical development of ellipsoidal coordinates" mean?

You are correct. I heard the argument that considering the WGS 84 coordinates as if they were measured on a sphere helped to reduce the computing time, which is usefull for Web Mapping, but I didn't ...
radouxju's user avatar
  • 49.8k
1 vote

Molodensky Transform with PROJ

Molodensky is a datum transformation, but you are using the proj application, which is used to projections. You can perform datum transformations with cct application instead (https://proj.org/apps/...
Gabriel De Luca's user avatar
1 vote

Are Tissot's indicatrices enough to tell whether or a not a projection will keep 3D lines also straight in the projected 2D space

A cartographic projection is a nonlinear transformation in two dimensions. So in the first place you must reduce the three-dimensional line to the mathematical surface on which the cartographic ...
Gabriel De Luca's user avatar
1 vote

How does Google Earth calculate the inverse geodesic problem, in particular the forward azimuth?

After two days I found the answer to that question myself. . I am not sure if I should just delete my post or leave it there together with this answer. Well, maybe someone else wants to know too. ...
Ralph Beckmann's user avatar
1 vote
Accepted

Derivation of initial bearing calculation

I was surprised that I didn't find this ready-made question and answer on this site. This formula is sometimes taken from http://www.movable-type.co.uk/scripts/latlong.html, which in turn is taken ...
Gabriel De Luca's user avatar
1 vote
Accepted

What's the name of the area between two geographic coordinates?

More informally than a spherioidal quadrangle, a much more common and useful term is "bounding box", sometimes shortened to "bbox".
alphabetasoup's user avatar
1 vote
Accepted

Calculating bearing (magnetic) between two lines?

Yes, there is something more to consider: the Magnetic Declination. This is a scalar variable, derived from a physical property: the Earth's magnetic field. It is variable dependant to location and ...
Gabriel De Luca's user avatar
1 vote

Height transformation parameters between any model and EGM-96

If you have a geoid model, that is often a set of equations to convert between gravity-related heights (elevations) and ellipsoidal heights. It's often modeled as a grid file. There are both versions ...
mkennedy's user avatar
  • 19k
1 vote
Accepted

Calculating Datum Corrections to Overlay pre-NAD27 USGS Maps?

Prior to NAD27 / North American Datum of 1927, US maps used the US standard datum AKA USSD. Starting at NADCON 5.0, the National Geodetic Survey (NGS) has started supporting transformations to and ...
mkennedy's user avatar
  • 19k
1 vote
Accepted

Name for meridians rotated 90 degrees about a meridian

They are oblique meridians, perpendicular to an oblique equator.
Martin F's user avatar
  • 8,956
1 vote

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

One example is the the International Terrestrial Reference Frame (ITRF). Each ITRF realization provides alongside its transformation parameters also its linear rates of change with respect to the ...
pinpon's user avatar
  • 174
1 vote

Moving dead ahead: rhumb line, great circle or none

So I found this question in a search for why the great circle route requires course corrections, and this post got me to my answer but didn't answer it directly. As what @gansub says, latitude circles ...
Jon Thompson's user avatar

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