Next, consider how much of the Earth your map will cover, and the general shape of the area of interest. The Miller Cylindrical is a compromise designed to give shapes similar to the traditional Mercator, but with less polar stretching. Curiosities Peirce’s quincuncial projection The Peirce quincuncial projection is an unusual projection of the globe into a square. It’s perhaps of greatest value as a curiosity. Even Argentina or Norway would not look bad on it, although they would probably show better with the Cassini projection. The Cassini projection is a good choice for an equidistant projection for instance, a Cassini projection with a central meridian of 80 degrees West produces an attractive map of the Americas. Below it, they will be stretched north to south.
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It ma;proj a compromise between equatorial and temperate regions but still gives considerable distortions at high latitudes. It is designed to be a good compromise for global political maps, since country boundaries anywhere in the world are reasonably clearly represented on it. Converts from the Gall-Peters cylindrical equal area projection. This package offers a great many projections, because no single projection is appropriate to all maps.
Tcl Library Source Code: mapproj – Tcl Library
The Miller cylindrical projection is an attempt to preserve the appearance of the traditional Mercator map while mitigating the most extreme distortions in the polar regions. It therefore allows the shortest path between two points to be plotted with a simple straightedge. Except for the fact that it gives a traditional look to the map, it’s not very useful; it’s perhaps best suited to maps that will be treated as works of art. Lambert’s conformal conic The Lambert conformal conic projection, like all conformal projections, preserves the local shape of maapproj areas.
The Robinson projection yields attractive maps for things like political divisions, but should be avoided in presenting scientific data, since other projections have moe useful geometric properties. The mapproj package provides a set of procedures for converting between world co-ordinates latitude and longitude and map co-ordinates on a number of different map projections.
mapproj: Map Projections version from CRAN
The ‘mapproj’ mapprpj in tcllib contains the conversions between geodetic See geodesy and map co-ordinates for a variety of map projections. Large areas having a primarily North-South aspect, particularly those spanning the Equator, need some other choices.
They also are useful for the polar regions where cylindrical projections are nearly useless and for special purposes such as antenna pointing and great circle navigation. The co-ordinates are relative to the center of the map sheet to be drawn, measured in Earth radii at the reference location on the map. Arguments The following arguments are accepted by the projection commands: Conic projections show meridians as straight lines intersecting at one of the Poles.
KBK Are you volunteering to add it to tcllib?
Above the standard latitude, landforms will be stretched east to west. Azimuthal projections and possibly the Cassini projection mapptoj the only really good choices for mapping the polar regions.
Tcl Library Source Code
Conformal projections include the Mercator, the Albers azimuthal equal-area, the stereographic, and the Peirce Quincuncial projection. Here is a review that attempts to illustrate some of the major points. The gnomonic projection is an azimuthal projection having the unique property that all great circles are represented as straight lines. The gnomonic projection produces a map on which all great circles the shortest distance between two points on the Earth’s surface are rendered as straight lines.
If slight scale errors are acceptable in your application, then any of the projections appropriate to large areas should work for small ones as well. If the data are directional e. The Dymaxion projection [ 1 ] is pretty cool: The Mercator projection is traditional, but the extreme distortions of area at high latitudes make it a poor choice unless a conformal projection is required.
Conic equidistant The conic equidistant projection has correct scale along any meridian. It is also effective for thematic presentation of large equatorial regions with a predominantly north-south extent; the Nile valley or even the whole of Africa would show well on it. The Robinson projection is neither conformal, nor equidistant, nor equal-area.
All projections are going to be compromises. Curiosities Peirce’s quincuncial projection The Peirce quincuncial projection is an unusual projection of the globe into a square. It shares with all conformal projections the problem that regions near the edge of the map have colossal area distortions. Choose the Lambert conformal conic, the conic equidistant, or the Albers equal-area conic according to whether shape, distance, or area are the most important parameters.
Bounty program for improvements to Tcl and certain Tcl packages. Below it, they will be stretched north to south. What scale is your map?