Hot answers tagged gis-principle
Geographic coordinate systems (lat/long) are based on a spheroidal (either truly spherical or ellipsoidal) surface that approximates the surface of the earth. A datum typically defines the surface (ex radius for a sphere, major axis and minor axis or inverse flattening for an ellipsoid) and the position of the surface relative to the center of the earth. ...
You will obviously get better answers from textbooks, but here is an simple explanation: Map Projection: It is a method for representing a spherical or curved surface on a flat plane. Datum: It is the reference or origin based on which measurements are made.
After struggling with this question ten years ago, and finding many confusing things written about the topic, I published a brief article in Directions Magazine that presented an answer as simply, plainly, and accurately as I could make it. The following is excerpted from that article. Reprojecting geographic features Two things must happen when you draw a ...
RADICAL CARTOGRAPHY showcases couple of really nice examples. My two favourites: Mississippi meanders Statistical Atlas of 1870 US Census
Eduard Imhof's work, especially his hand-drawn hillshading maps:
As the question does not specify that a map has to be a traditional static map, I would like to propose the Mapnificent London travel times map. As per usualy, Google are really pushing what you can do with Online Mapping APIs. In terms of map design, the v3 API now gives you greater control over tweaking the underlying base map. The map is also very ...
A couple examples of beautiful flow maps An article in the open journal PLoS, Redrawing the Map of Great Britain from a Network of Human Interactions by: Carlo Ratti, Stanislav Sobolevsky, Francesco Calabrese, Clio Andris, Jonathan Reades, Mauro Martino, Rob Claxton, Steven H. Strogatz PLoS ONE, Vol. 5, No. 12. (8 December 2010) Facebook worldwide ...
As scw points out, you want an implementation of α-shapes. Alpha shapes can be considered a generalisation of the convex hull. They were first described in 1981 in: Edelsbrunner, H.; Kirkpatrick, D.; Seidel, R.; , "On the shape of a set of points in the plane," Information Theory, IEEE Transactions on , vol.29, no.4, pp. 551- 559, Jul 1983 ...
Originally created and posted by Tear on the Cartographer's Guild Forum. A hand created map of George R. R. Martin's Westeros from The Song of Ice and Fire series:
Here is what you are looking for. You can download and test the program: (in java, under GPL license) The paper presenting the algorithm is there: Duckham, M., Kulik, L., Worboys, M.F., Galton, A. (2008) Efficient generation of simple polygons for characterizing the shape of a set of points in the plane. Pattern Recognition v41, 3224-3236
U.S. National Park Service Maps (from Getting Real: Reflecting on the New Look of National Park Service Maps):
Reykjavík Interactive Map
This is the one that started it all for me. At age ~10 I first read R.L. Stevenson's Treasure Island. The map somehow encapsulates the mystery, adventure, search and discovery of a great story. Not only that, but Pirates! Har.
wwnick's answer is correct, but it is a bit misleading in the sense that it emphasizes ellipsoid parameters and IMO understates the importance of 'the position of the surface relative to the center of the earth' - the NAD 1927 example needs to mention that the geodetic "center" of NAD27 is a base station at Meades Ranch in Kansas. One could have (and often ...
Here is a good one: The Atlas of Canada Map of the North Circumpolar Region http://atlas.nrcan.gc.ca/site/english/dataservices/wall_maps/MCR1-2.jpg/image_view Also interesting is the Cartographica journal article describing the work involved in putting this map together: http://utpjournals.metapress.com/content/d80604507k247v46/
I like interactive maps from Stamen a lot. Especially, for their their focus on handling temporal interaction. Examples: SF crimespotting Hurricane Tracker (Update) Surging seas A non temporal example: Watermark, Terrain and Toner tiles
There are a lot of great bad examples at http://cartastrophe.wordpress.com/. For example this map of Europe (part of a world map that uses colors excessively and without obvious purpose): Besides the coloring, the labeling on this map is a mess.
In 15 years of answering GIS questions on listservers and, now, Web pages, I have noted some recurring issues that suggest a need for practitioners to learn certain specific computing concepts. None of these are deep; all these are well known; but all seem to be common deficiencies in the background or understanding of a significant minority (majority?) of ...
My favourite maps are John Ogilby strip maps of routes within Britain. The originals are from 1675, though there was also an official reprint around 1700 I think. I have this one (the road from Hereford to Leicester) hanging in my office. I'd love to get a full atlas, but the cost would be rather more than I can afford! Truly beautiful, not to mention ...
Can't believe no-one has mentioned XKCD's Map of the Internet: and this one has some mind-blowing aspects:
This is pretty much an interactive map This is a truly wonderful thread for a maplover like me! I found this (with a little help from my friends) Rock and roll. Metal Map
Overlaying a huge amount of data without taking care of the readability makes such pixel blots: (some people pretend these "mashups" are the Cartography 2.0. Maybe not).
It's already explained in the terms: Triangulation = working with angles Trilateration = working with distances. In real world applications you work with both, or combine them. For example GPS Signals are rather trilateration concepts. Speed and time equals a distance which determines your position...
This seems to be a specific application of alpha shapes, which are from my reading a more general form of this problem. R has the alphahull module, which has excellent documentation on computing alpha shapes. Also check this detailed background on alpha shapes. If you only want to compute convex/concave hulls, check out lasboundary, part of lastools, it ...
From 2011 SND awards: Best printed map -NG ‘Gulf of Mexico’ map (PDF available here): Miguel Urabayen Award - NG ‘World of Rivers' map: (Interactive version here) (Via FlowingData blog)
This question assumes an ellipsoidal model of the earth. Its reference surface is obtained by rotating an ellipse around its minor axis (plotted vertically by convention). Such an ellipse is just a circle that has been stretched horizontally by a factor of a and vertically by a factor of b. Using the standard parameterization of the unit circle, t --> ...
From the hip my answer would be Stephen Walter's 'The island': witty, irreverent, slightly subversive he has hand drawn a map of London representing it as an island (poking fun at Londoners' London centric view of the world). http://www.bl.uk/magnificentmaps/map4.html I think its beautiful as its highly original, detailed, fascinating and I interpret it ...
Any software that can project coordinates accurately can compute accurate Tissot indicatrices. A good source for the formulas is Snyder, John, Map Projections--A Working Manual, primarily at pp 20-26. (I won't reproduce them here because this site doesn't have appropriate tools for communicating mathematical formulas.) They require all four first ...
Shanghai Interactive Map: Actually there are many other cities there drawn in such style. Use google translate ;) Very interesting renderer, quite good for interactive public maps I think.
Another example of cartographic bad design from a federal French agency (detail): http://www.developpement-durable.gouv.fr/IMG/pdf/DGALN_Repartition_des_reserves_mondiales_de_MP.pdf
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