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Questions tagged [reprojection-mathematics]

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0
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1answer
29 views

Warp a shapefile from transverse Mercator to Lambert projection

I'm quite a newbie in QGIS. I imported in QGIS a shapefile of a European country (as well as a TIFF representing the contour). These files are referenced in EPGS 3035. I would like to transform a ...
0
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0answers
17 views

Unwanted Flyback Lines In Azimuthal Equidistant Projection

After reprojecting a world polygon shapefile's vertices into Azimuthal Equidistant Projection, and trying to plot the resultant points as PolyLines, I find that some of my PolyLines can not longer be ...
3
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0answers
17 views

Accurate area calculation for countries worldwide individually [closed]

I have polygons of countries with its administrative divisions, I would calculate the areas of each division in a country accurately. I got the bounding boxes for each country, then I divided its ...
2
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1answer
37 views

Relation between scale factor and standard meridians/parallels

Let's use transverse Mercator with a custom zone, with central meridian 30, the zone is 3 degrees wide at the equator, with a scale factor k=1, it means that the cylinder touching the spheroid along ...
3
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1answer
55 views

Vizualise different projections of a vector using QGIS

How to vizualise different map projection for a vector layer at once with QGIS, then export the two forms as Geographic WGS84 e.g. I have a shapefile for Europe, how to vizualise it in CRS Lambert ...
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0answers
23 views

Create custom projection for Shapefile, given specific target coordinates [duplicate]

I have a somewhat odd situtaion. A client has provided me with a Shapefile that has no projection information, along with an image of the map that it corresponds to. I have run some coordinates ...
0
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1answer
35 views

Failure to re-project SpatialPolygonsDataFrame to Equidistant Cylindrical in R (units problem?)

I am trying to re-project a shapefile to match the projection and units o Black Marble nightlights data (link below) which comes in a raster with Equidistant Cylindrical projection, units in meters. ...
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0answers
24 views

Reprojecting a SHP in QGIS to used it in ERDAS

I´m trying to created a AOI in ERDAS with a shapefile, but this shapefile had a projected system different to system that my image has, because of that I changed the projected system of the shp in ...
2
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1answer
114 views

Lebanese army projection + datum to WGS84

Most public offices in Lebanon give their data out as Esri shapefiles, with a strange non-standard projection, making it very difficult to use with any data from other sources, including any data in ...
1
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1answer
33 views

Help understanding coordinates

I am trying to use this lightning data set. https://www.ncei.noaa.gov/thredds/dodsC/lightning/countPerYear_Aggregation.ncml.html i do not understand the coordiante system which was used in generating ...
1
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0answers
26 views

Orthorectification on a DSM

I would like to orthorectify on the features (trees and buildings), noted that with may cause some stretching or tearing on the image due to the obliquity of the look angle. I'm only interested in top ...
0
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1answer
42 views

projectRaster() result does not have the same nrow and ncol, but has same resolution

I have a land use land cover (lulc) raster in WGS84 coordinate system shown below class : RasterLayer dimensions : 59575, 57541, 3428005075 (nrow, ncol, ncell) resolution : 0.000509, 0....
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0answers
46 views

writeRaster() not writing datum information

I am trying to reproject a raster to the USGS version of the Albers Equal Area Conic projection. Following this post, which talks about projecting vectors by adding the +datum=NAD83 and writing it out,...
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0answers
38 views

Projection of raster to sinusoidal projection

I have my definitive raster shown below. This raster has the projection as mentioned here class : RasterLayer dimensions : 7276, 8330, 60609080 (nrow, ncol, ncell) resolution : 463.3127, ...
3
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2answers
129 views

How to change the coordinate transformation function in Oracle?

I'm trying to reproject some data from one CRS to another (SRID:27493 to SRID:3763) using the SDO_CS.TRANSFORM function. The function works and returns no errors, but the coordinate transformation ...
2
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1answer
99 views

Reprojecting XYZ coordinates in Python whilst keeping Z coordinate constant

When doing a reprojection from a projected coordinate system (e.g. EPSG:28992) to a geographic coordinate system (e.g. EPSG:4326), the Z coordinate gets an offset of 45 meters. The Z coordinates of ...
1
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1answer
70 views

What does it mean to reproject a satellite image from utm (zone 13N) to wgs84?

I'm trying to understand some legacy code that processes landsat satellite images. Source images are in UTM and they are reprojected to WGS84. I'm a GIS noob but I understand that WGS84 is a datum for ...
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0answers
50 views

Improving reprojection accuracy

Main question: how can I improve the accuracy of my reprojection? I am combining my dataset to a previous one, and I have chosen a different CRS: the previous one is in WGS 84 (EPSG:4326) and mine is ...
1
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0answers
27 views

Distance between points not consistent

I have an Openlayers application where I can input a centre point, width and height in meters from which I can generate a bounding box to display on the map. The problem I'm having is calculating the ...
2
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2answers
124 views

Reproject SRID using DotSpatial

I'm nota GIS guy so I need some help. I need to reproject from one SRID to another. I'm trying to take global lat/longs (4326), reproject them to a local SRID (2336). This is basically the line of ...
0
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1answer
143 views

Project UTM Coordinates to three.js Coordinates With D3

I've been working on an application where I am building a 3d terrain, using three.js. The part I have working so far is building the 3d terrain mesh from standard 30m elevation data, and then draping ...
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0answers
47 views

What is causing ogr2ogr to fail to merge shapefiles without a reprojection?

Update 23-04-2018 The main issue has been solved, I (incorrectly) assumed all the files would share the same crs. This isn't the case and zones UTM 13N to 16N are used. So with no target crs for ...
1
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1answer
185 views

Finding correct extent of projection?

It is tricky to manage the extent of a coordinate system when that extent is not an aligned rectangle in another coordinate system. For example consider Thursday Island, located at: 142.2°, -10.2° (...
2
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3answers
57 views

Aligning Coordinate System?

I have some DEM files that use a coordinate system that doesn't align well with WGS84. I can align them through the data frame properties -> Coordinate Systems Transformation, where i type Only the x,...
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0answers
21 views

Is there such a thing as no projection? [duplicate]

I was reading an article that said when we display a map in WGS84 many people call it no projection. But most definitely when you see the map it has been distorted on a 2D surface. Which got me to ...
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0answers
32 views

AssetFinda Plugin projection issues in QGIS

I am currently trying to overlay raster and vector data in a common projection as the Asset data which is using NZGD:2000 EPSG:2193. I have an ecw aerial image that initially loads as a generated CRS. ...
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0answers
122 views

Postgis st_transform precision

I am checking effects of reprojecting planar coordinates from one CRS to another and back, keeping the same DATUM, and I was trying to determine the cause of the loss of precision. I know that ...
4
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0answers
244 views

Re-referencing raster in rotated coordinate system by “de-rotating” it

My Trying to define a "rotated regular grid" coordinate system in QGIS question about this got closed because there was already an answer to it, which I understand. I went to the answer in ...
1
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0answers
33 views

Relocate points added into a layer with different EPSG than the orthophoto layer using as reference

Thoundsans of points, representing singular trees in a region, were added manually into a shape layer with EPSG:23030, but it was done following visually the images from an orthophoto WMS layer with ...
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0answers
46 views

Transformation from unknown projected system to WGS84 from known data points in qgis

I have a set of points with conventional (X,Y), supposedly projected coordinates (easting and northing). These X,Y data are just values in mm, measured on a paper map from some arbitrary origin point. ...
1
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1answer
175 views

How can I use the authagraph projection in QGIS?

I have only been able to find this resource which reproduces the authagraph projection and it is compiled in C. Is there any way I can use this resource to make an authagraph projected map in QGIS? ...
0
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0answers
57 views

Azimuth on projected tile map

Here is a very specific problem : I have some mercator flight simulator maps I projected with real coordinates. However, due to game simplification, these maps are not oriented correctly and real ...
0
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1answer
38 views

Save GeoJSON file in GCS

I'm trying to make sure that my geojson file saved from QGIS is saved in a GCS with lat lng points. When I open my file I get coordinates like this which seems like my file is saved in nad83 as ...
4
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1answer
122 views

Which method is better for accurate area measurement?

Input : I have my original data in 4326. This data spans across the globe. This data is collected from DGPS so its accurate to 1 inch. The data is in geometry as geography is costly and functions are ...
0
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0answers
29 views

Equal area projection

In which projection I should project a polygon of a country to get the right area in the attribute table without a distortion? For example greenland
2
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1answer
321 views

Earth engine reproject: why does reprojecting a pixel at 30m scale gives me pixels with an area of ~550?

Trying to understand how reproject() in Google Earth Engine works. To find an example, I am using ee.Image.pixelArea(), which gives an image containing the area of each pixel in square meters. Now ...
1
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0answers
176 views

Need a projection like Azimuthal Equidistant (AEQD), but with polar coordinates

I have a geotiff in a simple latlon projection. I want to reproject its data on a plane tangential to Earth ellipsoid to make some further calculations. Just now I'm using aeqd projection for it, but ...
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0answers
65 views

Cartesian / Meters issue while making ellipses

I am trying to create an ellipse to be stored in my django project. I'm provided a lat, lon, major/minor in Nautical Miles, and an orientation in degrees. Between this post and the docs I've been able ...
3
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0answers
313 views

Calculate lat/long as percentage distance between two points (MSSQL)

I've loaded the US road shapes into MSSQL. I've determined the query to locate the segment of road for a specific address. The segment contains a "linestring" from a series of points. I'm trying to ...
0
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1answer
129 views

Bizarre Long, Lat coordinates…don't make sense at all

I've tried everything I can including all the possible projection transformations....these lng, lat's make no sense. Here is a sample coord with its disclosed mapping. The point is in British ...
2
votes
1answer
755 views

Convert features from EPSG:3857 to EPSG:4326 projection not working OpenLayers 4?

I have a simple task to do, supposedly OL4 and format.GEOJson.readfeatures should do that automatically. But it doesn't. Remembering that is a FeatureCollection and has CRS set. I have a map with ...
14
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1answer
1k views

Understanding reprojection?

One thing that I can't quite get my head around is Reprojection. It comes up a lot in questions on Stack Exchange, and there are plenty of How to questions and answers about specific issues using ...
3
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1answer
683 views

Calculating the earth radius at latitude

This is an extension to this question: How do you compute the earth's radius at a given geodetic latitude? and to the Wikipedia page: https://en.wikipedia.org/wiki/Earth_radius#Geocentric_radius ...
3
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1answer
355 views

Create a polygon using GDAL to calculate the points

I wish to create a polygon that looks like this (it's a tree and a root scan): I have a file containing positions where readings have been taken, and I have the centre point and the projection. So, ...
2
votes
0answers
36 views

Working with intersecting polar grids

I'm having some trouble figuring out the best way handle some GIS data. I want to analyze pollution from specific sites at specific points. I have a list of sites I'm interested in all across the ...
1
vote
1answer
278 views

How do I get utm data converted into wgs84 all within Python27?

How do I get utm data converted into wgs84 all within Python27? Does anyone know how to import the QGIS Lyon 'reproject' tool I to Python27? I have a Python script that writes utm Into a text file ...
1
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1answer
139 views

How to describe a MODIS Tile's distortion

When looking at the MODIS grid [1] and compare it to how the sinusoidal projection is distorted, I wonder how to both practically and formally describe the distortion factor for each MODIS grid tile. ...
0
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1answer
248 views

Re-projecting ground control points of similar images (Georeferencing in QGIS)

I have several maps to digitize. The base maps were Canadian NTS map sheets, all for more or less the same region. The useful information has been traced on top with handwritten markings. The maps ...
0
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1answer
670 views

How to know what value use to convert meter in degree using Google Maps info [duplicate]

I am trying to create a mathematical formula to convert meters to decimal degrees. Reading this article Decimal Degrees, I thought this generic formula: x = (Value_in_meter * 0.00001)/1.1132 But I ...
6
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3answers
9k views

What is the formula for calculating world coordinates for a given LatLng in Google maps?

I want to calculate a given LatLng to the world coordinate . I know I can use the internal projection of Google maps like this: var map=new google.maps.Map(...); map.getProjection()....