Questions tagged [wgs84]

WGS 84 is a geodetic coordinate system, commonly referred to as EPSG:4326.

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127k views

Difference between WGS84 and EPSG:4326?

What is the difference between WGS84 and EPSG 4326? It seems like for a given dataset it might be both WGS84 and EPSG:4326.
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Map projection in OpenLayers

I want to overlay some data whose projection is WGS-84 on Google map layer in OpenLayers. But I just can't make them in the right place. I did as follows: map = new OpenLayers.Map('map', { ...
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Precision when working with spatial data in GIS

Is there a basic or introductory study that examines and compares the precision of spatial data when working with varying precison of the data input, like having 1, 2, ... decimal places? with the ...
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What causes the GPS offset/shift in China?

I've spent close to two full days trying to understand the nature of the infamous GPS shift in China. After sifting through the noise, two recurring symptoms are that: GPS coordinates (WGS-84) plot ...
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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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Converting between wgs84 and nad83

This is a newbie question that is about converting between wgs84 and nad83. I have aerial photos that I am trying to compute lat long coordinates for as closely as possible. There are several factors ...
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5answers
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What is projection of WGS84 in GIS software? [duplicate]

WGS84 is a reference ellipsoid that determines coordinates of every point on Earth using latitude, longitude and height about the its surface. This ellipsoid is often used as a base to make maps. ...
14
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Converting projected geoTiff to WGS84 with GDAL and Python

Apologies if the following question is somewhat stupid, but I am only VERY new to this whole GIS thing. I am trying to convert some projected geoTiff images to WGS84 using gdal in python. I have ...
14
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1answer
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How to find ring of coverage of GPS Satellite on WGS-84 ellipsoid?

Given the following: Time, t The set of IS-200 Ephemeris data, E, of a GPS Satellite corresponding to time t The ECEF position of the GPS satellite, P=(x,y,z), derived from the time and ephemeris, (t,...
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4answers
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Looking for a pythonic way to calculate the length of a WKT linestring

I was quite unsatisfied with Calculating Length of Linestrings in WGS84 in Miles. It kept me wondering if there is a more convenient, Pythonic way to calculate the length of a WKT linestring according ...
13
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4answers
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How do I calculate the bounding box for given a distance and latitude/longitude

I need to be able to calculate a bounding box or circle for a given WGS84 latitude and WGS84 longitude, and distance but have no idea where to start! The distance from the start Lat/Lon would be 10Km ...
12
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1answer
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Characteristics of different methods to convert ECEF to LLA

I'm trying to convert ECEF (Earth Centered, Earth Fixed) coordinates, which are defined in X,Y,Z, centered at (0,0,0) to LLA (Latitude, Longitude, Altitude). There are a couple of methods I found on ...
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1answer
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Point of Intersection for a Ray and Earth's Surface

Say I have a ray vector originating from somewhere out in space. An example might be a ray of light from the sun. How can I calculate the point of intersection (if it exists) between the ray and the ...
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Converting X,Y coordinates to lat/long using pyproj and Proj.4 returns the wrong coordinates

I'm writing a python script that reads multiple XML files containing x and y coordinates and combines them all into a single csv file. Latitude and Longitude are required fields in the csv, but I am ...
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2answers
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How are EGM96 and WGS84 related to each other?

As far as I understand the EGM96 defines the Geoid, where as the WGS84 Standard defines the Ellipsoid. Is the ellipsoid defined in the WGS84 standard defined in a way to maximize the congruency with ...
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Projecting EPSG:4326 data in 2D map?

I like to think I'm relatively well-versed in datums, projections, and coordinate reference systems. OpenStreetMap data is stored in WGS84 Lat/Lon (EPSG:4326). This CRS is geographic and therefore ...
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3answers
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How do I get the area of a WGS84 polygon in square meters?

The following gives me the area of the polygon in square degrees: SELECT ST_Area(ST_GeomFromText('POLYGON((871325.790874952 6105405.3261047,871418.748307692 6105359.72944624,871346.22022442 6105215....
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1answer
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Is re-projection needed from SRID 4326 (WGS 84) to 4269 (NAD 83)SRID

I have US census data against state boundaries stored as SRID 4269, in an MSSQL DB. The input data used for calculations against that dataset is stored as SRID 4326. As far as I can infer from the ...
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2answers
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Merge geojson polygons with WGS84 coordinate

I have a Geojson file with some adjacent polygons and I want to merge them into one. I know it's a recurrent question but I can't find information for polygons with latitude and longitude coordinates ...
9
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2answers
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Polygons across international dateline [-180..+180 longitude]

I'm trying to generate polygons for satellite orbital swaths. So far I have a method to generate two lines which represent the edge of each swath in [lat,long]. Some of the swath's cross the ...
8
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3answers
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Global grid, which reference system to use?

I have seen a couple global studies using WGS84 as geographic reference, with the problem that the area of raster cells is not constant. Which reference system would you use for a global analysis in ...
8
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2answers
784 views

Is a Helmert transform necessary to convert between WGS84 and NAD83?

I've read things all over the internet which claim that NAD83 and WGS84 are effectively equivalent (with minor ellipsoid differences). However, if I do geodetic (WGS84) -> ECEF -> geodetic (NAD83) ...
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How does a Spatial Reference System like WGS84 have an elipsoid and a geoid?

I found out that WGS84 is an ellipsoid with a "geoid component", but I'm unsure exactly how that can be. This is from PostGIS in Action, Second Edition (pg. 64), but it seemed a bit vague. ...
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Choosing UTM zone to use for large country?

I want to reproject OpenStreetMap roads data from the current projection (WGS 84) to UTM, since I read in another GIS SE Q&A(Getting $length in meters in QGIS?) that WGS 84 cannot be used to ...
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1answer
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Are these two OGC WKT projections the same? And if so, why are their reference strings different?

So here is the .prj text of a federal shapefile dataset of all public airports in its native OGC WKT format: GEOGCS["GCS_WGS_1984",DATUM["D_WGS_1984",SPHEROID["WGS_1984",6378137.0,298.257223563]],...
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How to recalc WGS84 Shape_Area field to square miles in ArcGIS 10

What are the units of the Shape_Area field in a wgs84 feature class? Is it decimal degree squared? I would like to convert that to something more meaningful like square miles without reprojecting the ...
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Which is the most accurate method of measuring distance?

I aim to analyse the accuracy of the various methods of geodesic calculations (distance between two points on Earth)based on the three assumed models of Earth - flat, spherical & ellipsoidal. I ...
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2answers
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java vividsolutions jts wgs-84 distance to meters

my (java) project uses com.vividsolutions.jts.geom, which provides a distance function. After some googling I finally found that the return value from this function is in central angle degrees, when ...
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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 ...
6
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1answer
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Should geometries be drawn using rhumb-line or great-circle paths?

I work with WGS-84 coordinates and, most of the time, my map display (luciadmap) is in Mercator projection. My client is surprised to see that, for a rectangular geometry: the line between the 2 ...
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Python script to convert Lat Long to ITM (Irish Transverse Mercator)

I am currently working on a python script that converts Lat Long (WGS84) to ITM. The formulas used are based on a paper published by OSGB (Appendix B): http://www.leica-geosystems.co.uk/downloads123/...
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1answer
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How to transform WRF Spherical Earth to WGS 84?

Weather Research Forcasting Model assumes a spherical earth model with a radius of 6370km. I'm looking to display the data onto the WGS-84 Ellipsoid model as that is the model my system uses for its ...
6
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3answers
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How to convert from EPSG:4326 to WGS84/UTM 32U?

I am unable to convert from the project's coordinate system to a different one using QGis 1.8.0. I have a .shp file with a certain coordinate system information (WGS84 EPSG:4326 according to qgis). I ...
6
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1answer
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Distances in {Plate Carrée projection - EPSG:4326 - WGS84}

"4326 is just the EPSG identifier of WGS84" [3] Indeed http://spatialreference.org/ref/epsg/4326/html/ says it is a GEOGraphic Coordinate System: GEOGCS["WGS 84", DATUM["WGS_1984", ...
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1answer
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Converting Lambert Conformal Conic to WGS84 using Proj.4

I am attempting to transform data from Lambert Conformal Conic lat/long and I am having some issues with the results. The shapefile I am attemtping to transform can be found here: http://tfr.faa.gov/...
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1answer
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What is the relationship between ITRF and WGS84?

Why are there people saying that "I am using WGS84(ITRF96)"? There are newer version of ITRF. Will WGS84 follow it? If so, what will be the influence to us?
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Measuring distance between points in ArcMap - what coordinate system to use?

This is a basic -newbie - question. I have some handwritten data points taken off a GPS - so I am assuming they are in WGS 84, and I want to load them in ArcMap 9.3, via excel, and measure the ...
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How does QGIS calculate distances when the data is not projected (WGS84)?

I am playing a bit around with Qgis 2.14.6 to understand how it deals with distance measurement. I took a line-shapefile that I saved in 3 different coordinate systems (4326, 32642 and a national one ...
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2answers
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Projected coordinate system for South America

Does anybody have any suggestions for a projected coordinate system for the Northern part of South America? I have a data set that reaches from Venezuela to Southern Peru and I'd like to do some ...
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1answer
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How to reproject MODIS Swath data to WGS84

Im new to GIS and now working with MODIS04L2 Aerosol Optical Thickness image. I need to reproject the image to other coordinate system such as WGS84 for later work but now Im stuck with it. I have try ...
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2answers
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Choosing projection for rasterization of random latitude and longitude data in northern Atlantic?

I have a dataset in the WGS84 geographic coordinate system that I would like to interpolate along a grid using Python. It appears gdal_grid is not available through the Python bindings, so I plan to ...
5
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1answer
170 views

Why is the length of one degree in Turf 0.9988?

Calculating the (spherical) distance along one degree of longitude at the equator in Turf returns a number less than 1 (Try it): require('@turf/turf').distance([0,0], [1, 0], { units: 'degrees' }) 0....
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Stereographic projection of WGS84 ellipsoid on a plane[python]

I would like to ask you for help in following task. What I need to do is to derive local x,y coordinates from latitude, longitude, applying stereographic projection of WGS84 ellipsoid on a plane, when ...
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4answers
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OSM To Postgis & WGS84 problems

I’m trying to import OpenStreetMap (OSM) data into postGIS it doesn’t appear to be working in that features do not appear to be in the correct place.. Using the QGIS OSM add in and a coastal shape ...
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2answers
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Generating polygon representing rough 100km circle around latitude/longitude point using Python?

Given a latitude/longitude point anywhere on earth, I would like to assemble a polygon that roughly resembles a circle with a 100km radius around that point. It doesn't have to be pin-point accurate, ...
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2answers
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Geographic Transformations in Alaska Between NAD83 and WGS84

I have done a ton of research on the most accurate transformation to use in mainland Alaska to convert between the NAD83 and WGS84 datums, but I just can't seem to find a definitive answer. ArcMap ...
5
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1answer
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How do I convert Eastings and Northings projection to WSG84 in geopandas?

I'm very new to projections and struggling to convert a map dataset from OSGB36 (Eastings and Northings) to WGS84 (lat/longs). I've used geopandas to import a shapefile. Now I want to export it as ...
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3answers
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Relation between Geoidal separation and antenna altitude in GGA sentence?

I have searched about definitions and relations about geoidal separation and antenna altitude reported in GGA sentence. The more I read the more I am confused.So in a simple manner can anyone explain ...
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Making Fishnet that is specific size in square meters on ground?

I have a raster image in GCS WGS 1984. For sampling I want to take a grid of 500 m^2 in my area of interest and pick the centroid of this square. How do I make sure that the grid created with Fishnet ...
5
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2answers
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How to calculate new point coordinates from distance and angle using ArcGIS SDK for iOS?

I want to calculate the coordinates of a new point. What I have: The source point coordinates, the distance (meters) and the angle For example: I want to create a point within 100 meters and 45 ...