Questions tagged [geodesy]
Scientific discipline dealing with the measurement and representation of the Earth's shape and gravitational field.
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Do different ellipsoids have different location of centre?
I wanted to understand how latitude and longitude of a location change by changing the reference ellipsoid. If the location of centre in 2 different ellipsoids is same, and they differ only in the ...
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Recommendation for a book for geographical distance calculations [closed]
I am currently writing my Thesis and I need a book covering the geographical distance calculation like haversine and Vincenty. Since I am not of this field, I can't find books which might help me ...
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Name for meridians rotated 90 degrees about a meridian
Let's say you drew lines similar to meridians, in that they all intersect at two opposing points--but instead of being at the poles, those points were instead somewhere along the equator.
Is there a ...
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Which of EGM96 geoid or WGS84 ellipsoid fits the earth better?
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If we separately add up |H| and |h| over the earth surface, which of the sums come out smaller?
Background
There is a phrase in the tag description of "ellipsoid" that says ".....
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Open Source Webmaps and Geotiffs
I have recently started to learn how to use open source web maps, and have come across the following issue.
When using geoserver and geo explorer (part of the open-geo-suite), I seem to get an ...
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PostGIS Geography Buffer producing different areas?
I'm trying to create circles of equal area in different places, but depending on the location of the centroid different areas are calculated. For example
SELECT ST_Area(ST_Buffer('POINT(0 0)'::...
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JTS Vividsolutions API: compute First (direct) geodetic problem
I'm using the popular JTS Vividsolutions API for Java. I'm struggling to find if I can perform calculation of the First (direct) geodetic problem with the API.
Is there a way to calculate this with ...
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Reverse Calculate Ellipsoidal Height
I have a few hundred points with ellipsoidal height taken a few years ago. Based on these ellipsoidal heights I had deduced orthometric heights for the same.
Is there a way to find the ellipsoidal ...
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How do you compute the earth's radius at a given geodetic latitude?
(I see there is an equation on wikipedia that does exactly what I am asking but there is no references. I have no way of confirming the validity of this equation!)
I already understand the difference ...
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How do I account for changing latitude with a spatial filter?
I'm working with data in latitude/longitude grid form in a non-GIS specialised package (MATLAB) and wish to apply spatial filters to it.
As this data contains a broad range of latitudes and is ...
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Which projection is suitable for the measurements of this great circle?
I have drawn a circle on google earth pro in such a way that its radius starts from earth center 0,0 (lat/long) and ends at 0,90 (lat/long). This circle divide the earth into two equall halfs as shown ...
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Does GPS correct for continental drift?
Does GPS correct for continental drift, and if so, how? (I'm mainly interested from the perspective of consumer devices such as smartphones.)
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Learning classical geography - recommended literature etc
I've been working in the field of GIS for a few years now, and there are some disciplines of knowledge where I lack a good degree of education.
My educational background is that I've studied computer ...
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How can I use ArcGIS 10.1 to find a geodesic equidistant point defined by three points?
For example, I have coordinates for three base points on a coastline and I need to find the coordinates of the point off the coast which is equidistant from all three. It’s a simple exercise in ...
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Given distance (in meters) what is the angle in geographic reference systems? [duplicate]
In QGIS and other systems sometimes I have a layer in geographic reference system (typically WGS84, EPSG:4326) and I'd like to calculate a buffer of say 5000m around a point.
So, given a point ...
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Trilateration on a Sphere, given 2 points and 2 distances
Given the points:
A) N 38° 38.000 W 90° 20.000
B) N 38° 39.000 W 90° 21.000
(I can calculate the distance between the 2 using a spherical earth model as 7710 feet, though it's not particularly ...
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Calculate geographic position based on azimuth, distance and height [duplicate]
How to calculate the geographic position of an object in sky (Point B)(like an aircraft) from Home Point (Point A) based on only four variables:
Lattitude and Longitude at Home Point, Azimuth at ...
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Scale on map requires correction coefficient. But why? [duplicate]
I am computing the distance of a map I am getting from ArcGIS' REST services by using a calculator as provided by this answer. In a nutshell, it uses a GeodeticCalculator for distance computation ...
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Technique for splitting raster image into tiles
I have written a standalone application which renders a globe similar to GoogleEarth/WorldWind which is currently able to display raster imagery from WMS servers. The native geodesy of this ...
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New coordinate system?
I just had my mind blown in answer to my previous question. I was going to rework that question, but decided it makes more sense to ask a new one.
I had been converting between ECEF and lat/lon, and ...
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Why not measure elevation from the center of the earth?
In trying to understand Geoid vs Ellipsoid height, I ran across this page.
One of the claims is:
Zero elevation as defined by Spain is not the same zero elevation
defined by Canada
Basically, ...
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Defining a line from geographic coordinate points.
On a flat surface we can define any point on line which passes from point1 (x1,y1) to point2 (x2,y2) via simple trigonometry.
How can we do that with latitude and longitude of 2 points?
Imagine we ...
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Intersection between a ray from lat, lon, alt, with pan, tilt and earth's surface
I have a problem that consists of finding the intersection point between a ray from a given lat, lon, alt, that is looking to a given pan and tilt angles and the earth's surface. I need the lat, lon ...
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Local Coordinate to Geocentric
The ultimate question, I need a transformation matrix to take a point in local space representing a roughly 500m x 500m place in New Mexico centered at -108.619987456 long 36.234600064 lat. The final ...
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What do different realizations of the same datum have in common?
Firstly, am I correct in assuming that the process of determining the shape and the size of the spheroid is independent from the process of determining the origin and the orientation?
For example, ...
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For a non-geocentric ellipsoid, how does the Lat/Long/Ell Ht & semi-major axis & flattening implicitly define the centre of the ellipsoid?
For example if we compare the AGD84 (Australian Geodetic Datum) with GDA94 (Geocentric Datum Australia), the centre of the AGD Datum is 200 metres different to GDA, because it is a best fit to the ...
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Long range Trilateration from 3 lat, long, range
I've been looking at the following solution to a similar problem
Trilateration using 3 latitude and longitude points, and 3 distances
However with my problem the 3 points are spread over a large ...
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How to generate geodesic linestring from two points in C#
I'm looking for a FREE C# class, library or set of functions that will allow me to generate a geodesic linestring (or array of vertices, whatever) from two decimal degree points.
I've found ...
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Which SRS is computational more effective to store continental scale data? (given some conditions)
For a Precision Agriculture application I need to make calculations in UTM projection. The data will be stored in Postgis and is made of soil samples results (point data) and field boundaries of many ...
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Attributes that characterize a geodetic track
I need a way to index and retrieve a large amount of track data. To do this I need to derive from every track as many attributes as I can. For now, I derive
Name
Tortuosity
Speed (average, max)
...
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How do you find a lat/lon (DMS) on a paper map using a 30cm ruler?
How do you use a 30cm ruler to find DMS on a paper map? The locations I would like to find are the 'corner' points so I can generate an extent based on the four corners.
I have an old paper map (3 ...
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Is there a geodetic benchmark that is fixed with respect to plate tectonics?
I see that NGS benchmarks are used to monitor the movement of geologic plates.
Is one of the benchmarks assumed to be in a fixed location, with movements of all other benchmarks measured with respect ...
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