A map projection is any method of representing the surface of a sphere or other three-dimensional body on a plane

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World map projection with United States in center

I am creating a map showing flight paths originating in the United States and traveling to Asia and Europe. I need a projection for the world that will focus the United States in the center of the ...
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3k views

Better Distance Measurements in Web Mercator Projection

I am working with an ESRI stack, storing my layers in a sql-spatial-enabled-SDE- geodatabase (Geometry type, Web Mercator-3857). I am building a web mapping application, so by default, the tiles are ...
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516 views

Is there a way to draw a straight line on a map which also represents a straight line on the earth surface?

I'm trying to understand more on projections. In this example, why must one calculate the curvature of the earth (great circle) if the map is already projected? Is there a way to draw a visibly ...
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3k views

Derive WGS84 Longitude & Latitude from British Northings & Eastings

I'm looking for a fairly simple way to append columns with WGS84 longitude and latitude to a table containing northings and eastings. The source data is Ordnance Survey's CodePoint Open, which I is ...
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Measuring distance in spherical Mercator vs zoned UTM

I've got points in WGS84 lat/long and I'd like to measure "small" (less than say 5km) distances between them. I can use the haversine formula from http://www.movable-type.co.uk/scripts/latlong.html ...
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What is the standard Mercator projection?

I'm using QGIS in order to re-project a shapefile I have into "Mercator" so that something like protoviz understands my co-ordinates. Protoviz tells me "Mercator" ...
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3answers
261 views

A global, grid-like projection for creating heatmaps

I'm putting together an application where I need to create a vector grid which will be used to store and display a heatmap. It has the following requirements: Can cover the entire planet. The vast ...
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306 views

How do I perform a 3 parameter geotransformation and projection in Sql Server 2012?

I have a table with latitude longitude (NAD27) columns in it. I compute two other columns, X and Y, representing Web Mercator (WGS84) location. Currently I'm using a Arcmap to do this, by applying ...
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496 views

An example Tissot ellipse for an Equirectangular Projection?

I am trying to calculate distortion of an equirectangular projection via Tissot indicatrices. I have tried following the directions on this post (among other things) but it is beyond my understanding ...
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573 views

What happens to feature class when importing to feature dataset?

I am creating a model that needs to ensure that all input datasets end up in the same coordinate system (among other things). I was originally going to batch project all of the datasets whether they ...
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7k views

Which is the correct projection in ArcGIS for EPSG:3857/900913?

I want to publish a mapservice in ArcGIS server, which will be overlayed on Google Maps or Bing Maps. For this, the Map Service needs to be in EPSG:3857/900913. The Google Maps projection is supposed ...
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1answer
197 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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156 views

How do ESRI and QGIS calculate scale values of geographic projections? [closed]

Does anyone know how (from which location) scale values are calculated in ESRI products and QGIS for geographic projections? The only thing I've noticed is that QGIS is changing scales when you pan ...
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6answers
1k views

Real-world example of Affine Transform?

From the Wikipedia article: In geometry, an affine transformation or affine map or an affinity (from the Latin, affinis, "connected with") between two vector spaces (strictly speaking, two affine ...
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3answers
985 views

Distance measurements across UTM zones: use geographic or planar approaches?

I have a survey grid spread across 3 UTM zones (36N, 36S, 37S). I want to find the nearest (or shortest) distances of the centroids of these grids to roads and various points between. It seems like ...
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769 views

What kinds of line segments/edges require high accuracy in a true surface-of-the-ellipsoid representation?

I've been musing (and doing prototype coding) for a 'projection free' geographic codebase with your basic point, line & polygon primitives. Rather than dealing with all the sacrifices that come ...
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399 views

How to get a “classical” globe projection

I have a shapefile of the world continents in EPSG 4326. To what reference system do I have to reproject my file to get a projecting like this globe below?
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502 views

Why are there both square and rectangle world maps?

When i search for images of earth divides to longitude ans latitudes seems that the are 2 major types: is a perfect square and the latitudes in it are grow a different rate from the equator to up ...
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471 views

Where did the polygons go after projecting a map in QGIS?

I'm fairly new at GIS know-how, but I've run into a problem with a projection of a world map. I have a shapefile of all countries I downloaded from Natural Earth. After projecting it into a ...
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634 views

How do I rotate the OSM map before printing?

What is the simplest way to rotate and render Openstreetmap data, and still get a nice render? For example Toronto, would fit best rotated slightly on a page in landscape mode, so the northern ...
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2answers
418 views

how to produce a Peirce quincuncial map?

As far as I know neither PROJ4 nor ESRI tools can apply the Peirce quincuncial projection. Does anybody know what libraries/softwares can manage it?
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1answer
683 views

QGIS- “On the fly” projection ON by default?

In QGIS 1.6, can users set "on the fly projection" to be checked ON by default (at application launch)? I know how to turn it on, but some users find they use it more often than not, and would like ...
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1answer
309 views

Using customized Coordinate System for Archaeological site data

I don't know so much about coordinate systems... In my office we use to deal with spatial data coming from archaeological sites. Each site has its own x-y-z coordinate system (GCS). Three simple ...
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683 views

How to define Winkel Tripel in proj 4.8.0?

I have QGIS with proj 4.8.0 installed. I'd like to add Winkel Tripel projection which seems to be defined as +proj=wintri But that definition string does not work. Is this a bug in my proj version, ...
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2answers
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Is it possible to reproject spatial data using SQL Server?

SQL Server takes an SRID when creating spatial data, but is it possible to retrieve an object as a different spheroid? For example, let's say I have a bunch of spatial polygons using SRID 4258, but ...
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730 views

Is the quadrilateralized spherical cube map projection the same as Snyder's cubic equal area map projection?

Is the quadrilateralized spherical cube map projection [1] the same as Snyder's cubic equal area map projection [2]? I know both are equal area polyhedral map projections ( ...
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Calculate distance in km to nearest points (given in lat/long) using ArcGIS DEsktop and/or R?

I have two point datasets in ArcGIS, both of which are given in WGS84 lat/lon co-ordinates and the points are spread across the whole world. I would like to find the nearest point in Dataset A to each ...
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2answers
2k views

How is EPSG:4326 data 'projected' in a 2D map?

I like to think I'm relatively well-versed in datums, projections, and coordinate reference systems, so if this is a stupid question I will suffer eternal shame. OpenStreetMap data is stored in WGS84 ...
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1answer
260 views

Can I just swap out a .prj file to reproject a shape file?

I'm an experienced software developer -- but a GIS noob. I have a shape file that I am trying to turn into a SVG map with Kartograph. When I try to run Kartograph I get this error: ERROR 6: No ...
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2answers
306 views

Should point data be equidistant projected when using ArcGIS IDW spatial interpolation?

I am wondering if anyone can clarify whether point data should be projected to an equidistant projection when using ArcGIS IDW spatial interpolation? I am working on a dataset from Western North ...
7
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2answers
616 views

How to determine projection parameters when customizing a projection

I am trying to customize an Albers and a Hotine Oblique Mercator (HOM) projection to minimuze distortion in the region I am analyzing. The region extends from about 51 to 62 degrees latitude, covering ...
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450 views

Method to generate points in any projection

I am writing an application in ArcMap to generate a grid of points. These points have a very defined layout and I have worked out an algorithm that works great under a projected coordinate system. ...
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use proj4 to specify Robinson projection with R ggmap and ggplot2 packages?

I want to project this map in robinson projection: library(ggmap) world <- map_data("world") ggplot() + geom_path(data = world, aes(long, lat, group = group)) ...
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1answer
4k views

What is the default projection in Leaflet?

I've read an API documentation for Leaflet on its site, but I can't realize: what is a default projection to view maps? It was written about spherical and elliptical Mercator and Equirectangular - so ...
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2answers
711 views

Bertin 1953 map projection settings

I am trying to use the Bertin 1953 map projection, as described in the book "Semiology of graphics" by Jacques Bertin. But I can't find the settings in any of my GIS software. Does anybody have a ...
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3answers
153 views

What coordinate system is this netCDF raster?

I obtained a netCDF raster file, but I couldn't get any metadata to get the name of the coordinate system the raster has been built on. The raster itself doesn't have any coordinate system embedded. I ...
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1answer
146 views

What are the pros and cons of forcing square pixels on reprojection?

I am using Erdas Imagine 2014 to reproject 4-band raster data from GRS 1980 NAD83 Lambert Conformal Conic (ft) to UTM GRS 1980 NAD83 North UTM Zone 11 (m). Unlike ArcGIS, Erdas provides the option to ...
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2answers
94 views

Best practices and examples of web maps of polar regions

I am looking for examples of web maps focusing on polar regions (Arctic or Antarctic) preferably using a polar projection. What could be best practices to follow for such web mapping applications? Any ...
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174 views

Which training courses in Geodetics can you recommend?

Can anyone recommend any training courses in geodesy which would cover the following objectives: Case studies on coordinate issues Overview of geodetic datums, coordinate reference systems and ...
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191 views

Geotransformation for polar stereographic?

I'm currently working to import CANGRID climate data (provided as Surfer Grid ascii, ".grd" files) into ArcGIS. The grid is 95 rows by 125 columns in size.Metadata provides lat/lon of origin (lower ...
6
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3answers
578 views

How does ArcGIS determine which transformation to use when projecting on the fly?

How does ArcGIS determine which transformation to use when projecting on the fly? Where this would come in would be going from NAD 83 to WGS 84. Multiple transformations could be considered so how is ...
6
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3answers
4k views

Why don't my Shapefiles and OSM data overlap in Quantum GIS?

So I'm pretty new to GIS, and I'm working on a mapping project using data for Vancouver, Canada. I want to combine Open Street Map data along with data provided by the City of Vancouver. But the City ...
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5answers
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OpenLayers: ALL image layers are out of place on google maps v3 and OSM base layers

Summary: I have 2 different image layers that looked fine with my old mapstraction/google maps based system. Using the same coordinates as bounds in openlayers results in a shift to the north by like ...
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2answers
381 views

What projection does the global climate region map from Wikipedia use?

I would like to use this global climate region map from Wikipedia as a "basemap" (by plotting over the image in R). Is it possible to determine the projection of this map?
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4answers
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How to reproject base layers in OpenLayers?

The issue is: I have vector/topo/image tiled maps for some places in north america which were published as ArcGIS Server REST service. These maps (A) are based in EPSG26912 projection. Now I wanna ...
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2answers
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What's a good toolchain to reproject some PNGs in plate carre to UTM?

I have some PNGs produced from Canadian DEM data. They're 1201px by 1201px heightmaps. Each one represents one quarter of a degree latitude and one quarter of a degree longitude. But I want to work ...
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106 views

Why has an orthographic projection been used in this NatGeo map?

I'm wondering why this maps uses an orthographic projection, resulting in 3 maps to view the whole world. What were the requirements or the reasons to choose this projection (why not Mercator ) ? ...
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1answer
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How can I transform GCS_North_American_1983 to GCS_WGS_1984?

I posted a thread today describing a shift in some of the NRC data (not all). Apparently, this shift has to do with conversion between Geographic coordinates, latitude and longitude and Transverse ...
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3answers
369 views

How can I obtain the same area values provided by the Census for TIGER boundaries using PostGIS functions?

In PostGIS, how can I compute the area of Census Boundaries and obtain the same results as are provided by the Census? For example, most Census Boundaries include attributes for Land Area and Water ...
6
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2answers
2k views

what is the best way to programmatically convert between WKT and Proj4 string?

some shapefiles have a .prj file associated with it. and the .prj file contains the projection info of the shapefile in the format of WKT. Sometimes I need to convert WKT to proj4 string, and ...