# 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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### 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]...
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 ...
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 ...
16k views

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. ...
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 ...
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### 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 ...
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### 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 ...
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 ...
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 ...
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 ...
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 ...
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### 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 ...
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### 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 ...
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### 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 ...
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. ...
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### 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/...
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### 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, ...
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### 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 ...
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 ...
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),...
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 ...
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 ...
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### 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> ...
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### 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, ...
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### 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 ...
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"]], ...
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 ...
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### 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 ...
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 ...
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 ...
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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### 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 ...
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### 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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### 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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### 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. ...
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 ...
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### 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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### 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 ...
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 ...
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### 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 ...
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### 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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### 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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### 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 ...
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### 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 ...
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 ...
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 ...
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? ...
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, ...