Questions tagged [mercator]

The Mercator projection is a cylindrical map projection presented by the Flemish geographer and cartographer Gerardus Mercator in 1569.

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18
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1answer
2k views

How does what3words build a grid of squares on the surface of the Earth?

What3words built a grid of squares of 3m2 on the earth. Does anyone know what is the algorithm ? I started with this method: the range of longitude is [-180, 180] and the range of latitude is [-90,90]...
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1answer
14k views

Calculating distance scale factor by latitude for Mercator

This was really inconvenient topic to google out - so I'm asking for clarification, did I understood things correctly. I'm talking about measuring short distances in Mercator projection (3857). You ...
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3answers
3k views

How did sailors navigate before the Mercator projection (1536)? [closed]

The Mercator projection (1536) must be great for nautical navigation. It allows one to find a bearing and keeping this constant one should reach the target (if not in the shortest line). But how did ...
10
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3answers
16k views

Adding additional geometry column in PostGIS?

I'm importing many sets of geodata into PostGIS, and they have different SRID's. (Some have EPSG:3857, some EPSG:4326, some something else). I'd like to create an additional geometry column, eg. ...
9
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1answer
301 views

Mercator bias plot in Leaflet

I was inspired by this wikipedia image from the mercator projections page to hack around with leaflet. The idea was to interactively have your cursor move a continent and that it would be corrected ...
6
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2answers
3k views

What's the accuracy of Web Mercator EPSG:3857?

Are there any references on the accuracy or (min/max/avg) error of Web Mercator when it comes to e.g. distance calculations? For the sake of completeness, I haven't found any reference to the ...
5
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2answers
11k views

Making geotiff and reprojecting to EPSG:4326 using GDAL?

My goal is to download a gif file from this webpage: http://aviationweather.gov/data/iffdp/2104.gif Then crop it to the known latlon bounds of 75N,45S,35W,70E, convert to geotif, and then project to ...
5
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3answers
7k views

Mercator: scale factor is changed along the meridians as a function of latitude?

"In Mercator projection the scale factor is changed along the meridians as a function of latitude" How to calculate the Mercator scale factor as a function of the latitude in decimal degrees ? I ...
4
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1answer
5k views

Re-project raster image from Mercator to Equirectangular

I have a raster image of the world map in Mercator projection, square 1:1 format. I want transform the image into an Equirectangular projection accurately. I assumed from my research that GDAL would ...
4
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1answer
724 views

Converting EPSG to D3.js

Given an EPSG projection (say, this Alabama one: http://spatialreference.org/ref/epsg/26729/) How can you take the given WGS84 projection bounds in such a way that you can use them in a D3.js ...
4
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1answer
372 views

How to center a user-defined CRS on an area of interest?

My study extent in central Iran straddles two UTM zones (39 and 40): I would like to create a user-defined CRS in Transverse Mercator projection with central meridian inside this area. Through ...
4
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1answer
3k views

Re-projecting from Polar projection to EPSG:4326?

I simply want to project a polar stereographic raster (EPSG:3411) to Mercator (EPSG:3857) or WGS84 (EPSG:4326). The data I is from NOAA. $gdalwarp -s_srs EPSG:3411 -t_srs EPSG:3857 northpsg.20141027 ...
4
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2answers
1k views

Using pyproj and Mercator: x_0=0 and y_0=0?

I'm having a hard time figuring out how to project correctly from a Mercator projection to LAT/Lon. Basically, I have a netCDF file with the following variables: LON0 = 42.0 => reference longitude ...
4
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1answer
1k views

Transforming lat and long to Mercator x and y

I've been trying to plot a set of lat and long coordinates to a Mercator map using the following set of equations: x = long - long0 y = ln(tan(pi/4 + lat/2)) These equations are from a page on ...
3
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1answer
3k views

Pseudo-Mercator projection with Decimal Degrees?

Hope this isn't a duplicate, did some searching but none seemed quite the same. Projection I want: WGS84/Pseudo-mercator. Selected. Looks Great. Canvas units I want: Decimal Degress. Selected. ...
3
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1answer
4k views

Mercator projection: formula for latitude based on pixels?

I am basing this question on knowledge from a previous one: Mercator projection: problem with latitude formula In that question/answer, the formula is given for working out how many pixels above/...
3
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1answer
362 views

Using project / layer CRS in QGIS?

I'm using QGIS 3.4.1, and I'm trying to print 61km x 61km area map of somewhere South Korea. Then I need to send this map with west / east latitude and north / south longitude info to other person, ...
3
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1answer
1k views

How to quickly change EPSG in QGIS (Openlayers; 4326 vs. 3857)

I'm using Qgis 2.12.2-Lyon on Ubuntu 14.04 LTS. With the OpenLayers plugin I added some OpenLayers to my Canvas. I usually use the WGS 84 (EPSG:4326) projection for my project, but I have to switch ...
3
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1answer
294 views

gdal2tiles pixel shift in output tiles

I would like to re-calculate large geotiff files (10,000 x 10,000px) with the help of gdal2tiles into little (256 x 256px) tiles. The process works fine. However, the result is not perfect. There is ...
3
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1answer
1k views

How a draw a circle (on the surface of earth) on a mercator projection?

I would like to use R and leaflet to draw a circle (a real circle on the surface of the earth) on a mercator projection. In the following code, I have the center of the circle (with lng=0 and lat=60),...
3
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1answer
649 views

Which projections emphasise the Northern Hemisphere, other than Mercator?

I'm working on a project where I have data points in the UK, US, France/Italy, Hong Kong and Japan. I want to show a world map with mini charts at each of these locations. For this project, it makes ...
2
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2answers
111 views

Why maps package adding straight lines in North America using mercator projection in r?

Why is this code creating a bunch of lines crossing the map? map(database = "world", proj="mercator", fill=FALSE, bg="white", resolution=0) How can I remove it without changing the ...
2
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1answer
2k views

Converting GPS Positions to Google Maps

I have a set of GPS-coordinates in a database, which I want to compare to a coordinate supplied by the html5 location API. My coordinates look like this: <WGS84Coordinates> ...
2
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3answers
4k views

Calculating Mercator coordinates from lat/lon

I am new to GIS but I am working on a project mapping a building using floor plans and JOSM. Using the PicLayer plugin I added the .png floor plan as a layer. I wrote a .cal file to set the scale, ...
2
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1answer
3k views

Converting x,y on mercator to WGS84 latitude and longitude

How do I convert a particular point on a Mercator map (points in a Mercator map svg) to WGS84 coordinates? Is it simply a direct translation of the x,y values, using a multiplier which matches the map ...
2
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1answer
277 views

projecting onto Cartographic coordinates using Gauss Conformal Mercator in python

The shapefiles and boundaries I work with are on WGS 84 referenced to SA: GEOGCS["WGS 84", DATUM["World Geodetic System 1984", SPHEROID["WGS 84", 6378137.0, 298.257223563, AUTHORITY["EPSG","7030"]], ...
2
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1answer
267 views

Angular rotation using Proj4, for local coordinate system

I have a polygon feature on map to which I need to transform the coordinates to local coordinate system with respect to new origin while keeping the same datum. So far using the Proj4 library and by ...
2
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0answers
152 views

QGIS Qtiles from EPSG 3395

I am having issues while converting my layer from 4326 to 3395. My Qtiles does not make tiles. I have a source mapinfo in 4326 with long, lat pairs. My goal is to show this on a maps.yandex (3395 ...
2
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1answer
763 views

Map scale factor when converting from Mercator to Equirectangular

Lets say I have a map in Mercator projection, and I know top and bottom latitudes: topLatitude = 80; bottomLatitude = -55; I also know width and height of a map: width = 800; height = 500; I want ...
2
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1answer
636 views

Overlay a raster image using Equirectangular projection (lat/lon) onto OSM/Google map with openlayers?

I have a forecast map of 6x6 lat/lon extend from 104E-110E, 10N-16N as an static PNG image and want to make it an overlay on the basemap of OSM/Google map using openlayers 3. The problem is OSM uses ...
2
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0answers
458 views

Calculating planar distance based on point coordinate and geodetic distance?

Using ThinkGeo, I have a Lat/Lon coordinate, and a distance of .1 miles. The .1 miles represents the radius of a circle and I'm trying to draw this radius around the lat/lon coordinate. The map units ...
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2answers
2k views

Mercator vs. Web Mercator for Large Scale Topographic Maps

I have 8 terabytes of imagery that is in either lon/lat or UTM projection that I will be using for the basis of large scale topographic maps. I have been studying the differences between Mercator and ...
1
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1answer
40 views

Straight lines plotting as curves

I'm trying to do something really simple, plot a rectangle using psxy on a .cdf grid file. Something like: grdimage grid.cdf -JM20c -R-70/0/20/60 -Bf20g10 -K > image.ps psxy rectangle.dat -JM -R -B -...
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1answer
2k views

Converting mercator meters without UTM zone?

I've been attempting to extract track information from Humminbird (Side Imaging Sonar) binary files and have hit a stumbling block with the coordinates it provides. The values are apparently in ...
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2answers
136 views

Historical maps as cylindrical projections

Objective: I want to overlay old, historical maps on top of Google Maps. According to Wikipedia, Google Maps uses a variant of the Mercator projection, a close relative of cylindrical projections. ...
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2answers
973 views

Why does Transverse Mercator projection have scale factor?

Why does the Transverse Mercator projection have a scale factor in ArcGIS and the standard Mercator projection not? In other words what is the difference between these two projections beside being a ...
1
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1answer
79 views

gdaldem hillshade stop working with new projection?

Parallel to gdalwarp `-te -5.8 41 10 51.5 -ts 1980 0` not working with mercator? , my hillshade works with lat/long input : gdaldem hillshade input.tmp.tif shadedrelief.tmp.tif -s 111120 -z 5 -az ...
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2answers
4k views

Proj4js Problem in converting coordinates from google mercator

I am a really beginner into web-cartography, so sorry if this subject is rudimentary or basic but I truly search for a long time and I am still stick in it. So the problem is: I don't understand why ...
1
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1answer
321 views

image rectification with Mercator projection

I have written an image rectification function which allows a user to select 2 points on an image and 2 points on a map. The function will then rectify the image so it is translated, scaled and ...
1
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1answer
243 views

how to compute tile row from latitude in mercator projection

I work on google tile images. I want to compute a tile row from its latitude. How can I do that. I know that tile system cover all of the earth from -85 latitude to 85 latitude. 4 tiles exists at the ...
1
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1answer
114 views

Mercator - create uniformly distributed dots over map

I have a map in Mercator projection. I know coordinates of corners. I want to render uniformly distributed dots to map. for (float latDeg = startLatDeg; latDeg <= endLatDeg; latDeg += stepLatDeg){ ...
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1answer
783 views

Formula of mapnik bounding box (spherical mercator)

I want to implement a tile server and I'm following the code in the repo node-mapnik-sample-code. When a request is sent with the parameters x, y, z (longitude, latitude, zoom), those parameters are ...
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1answer
6k views

How to make a point from real latitude and longitude values

My program has a center point and one moving object . At this moment this point is somewhere in Europe.But Now i have to change that point from the latitude and longitude values(of Australia) . Please ...
1
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1answer
550 views

Fixing mercator coordinates that are outside the world bounding box?

I'm using mercator-projected overlays from a crowdsourced website where volunteers georectify images of maps by hand. Unfortunately, the slippy map that serves as the site's interface wraps and allows ...
1
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1answer
583 views

Improving accuracy of mercator meters conversion to lat/lon?

My question is an extention to Converting mercator meters without UTM zone? While the answer in the previous Q&A got me so far, I've now come to an impass. While the conversion I do from Mercator ...
1
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1answer
255 views

osm2pgsql missing coordinates

I am quite new to GIS and OSM and am trying to get my head around exporting custom OSM region and uploading them into PostgreSQL. I have started with a very small map area to export with only two ...
1
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2answers
911 views

Compute the latitude of a center of mercator projection

Say I'm looking at a portion of a map that's displayed using Mercator projection with the view bounded at 40°N and 20°N. How do I compute the latitude of the point that's in the centre of that view? ...
1
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1answer
63 views

Converting X and Y coordinates from Mercator world map (square) image to Latitude and Longitude

I'm using the following JS to transform Latitude and Longitude to X and Y coordinates but now I need the contrary, transforming Latitude and Longitude to X and Y. export const latLon2xy = (lat, lon, ...
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0answers
284 views

Map camera image onto sphere

How would I determine what the red point (phi', theta') is for a camera oriented at a known (phi, theta) is from a given image? The point of this is to determine what (dphi, dtheta) is so that I can ...
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0answers
90 views

Problem with parseWKT : projection mercator-2SP

1 -CoordinateReferenceSystem crss = CRS.parseWKT("PROJCS[\"Mercator\",GEOGCS[\"WGS 84\",DATUM[\"WGS_1984\"," + "SPHEROID[\"WGS 84\",6378137,298.257223563,AUTHORITY[\"EPSG\",\"7030\"]]," ...