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Geographical data analysis

  • To: mathgroup at smc.vnet.net
  • Subject: [mg9565] Geographical data analysis
  • From: "TAZ" <ya_right at no_spam.com>
  • Date: Thu, 13 Nov 1997 01:40:27 -0500
  • Organization: i2020 -- Richmond's internet partner. http://www.i2020.net
  • Sender: owner-wri-mathgroup at wolfram.com

Plz send replies to gjmoyer at NOSPAM4u.net, remove nospam...

All my maps are controlled by vectors with x and y coordinates
(latitudes and longitudes (degrees with decimals)). The vectors shapes
polygons that again constitutes geographical area types for instance
municipalities or woodland or lakes or whatever. I would have thought
there from universities or elsewhere might have been an enormous amount
of freeware with utilities for dealing with the mathematics of
geographical data but have only found an old 1973 thing. I am in
desperate need for some utilities that I have no knowledge to make
myself, but also other utilities might be welcome.

The one I mostly need is a utility that can take two polygons decide if
they overlap and give me three or more polygons that contain areas from
polygon 1 area from polygon 2 and areas for both polygon 1 and 2.

For instance i could have one polygon describing Lake Ontario and
another describing the state Ontario. The results I need are: 1) 1 or
more polygons for the part of lake Ontario that is within the state of
Ontario 2) 1 or more polygons that form the part of Lake Ontario that
is outside the state of Ontario(if that exists). 3) 1 or more polygons
that form the part of the state of Ontario that is outside the lake of
Ontario(if that exists).

The next important wish is a utility that can calculate areas from the
vectors.

Also I need a utility that can analyse a polygon and decide if it is
described clockwise or counterclockwise. Utilities that can transform
from Mercator projection (which my data in reality are) to other
projections as "Lambert" would also be welcome.

Example of polygons:
90,67,8.406851,57.381565
8.603993,57.355554
8.623441,57.350039
8.637969,57.349599
8.645163,57.347066
8.64548,57.340508
8.654961,57.337411
8.655435,57.328042
8.648237,57.325048
8.644299,57.314838
8.646252,57.309215
8.655546,57.296375
8.654706,57.282229
8.641305,57.274834
8.638686,57.269214
8.637862,57.262656
8.628066,57.260129
8.623002,57.254884
8.623,57.251511
8.609941,57.243925
8.614995,57.235492
8.621192,57.232586
8.617921,57.218346
8.594279,57.204482
8.579126,57.191832
8.565764,57.191829
8.536095,57.199032
8.511332,57.201025
8.510999,57.201051
8.510256,57.201184
8.466794,57.20891
8.456684,57.209555
8.42077,57.219909
8.414718,57.224023
8.400671,57.228311
8.373364,57.240165
8.33807,57.247967
8.326815,57.247006
8.294416,57.258456
8.276465,57.257661
8.240441,57.270026
8.231858,57.276629
8.222842,57.283562
8.202207,57.288839
8.195778,57.294629
8.191674,57.29649
8.189065,57.295919
8.184774,57.300122
8.181634,57.303579
8.186463,57.310905
8.191366,57.311015
8.197966,57.321532
8.195942,57.327805
8.204486,57.340671
8.203271,57.346161
8.200381,57.359213
8.201474,57.381708
8.196637,57.390783
8.197666,57.402875
8.207576,57.429333
8.221999,57.448212
8.23218,57.457006
8.2404,57.464102
8.249946,57.480527
8.253857,57.484192
8.249684,57.492428
8.249815,57.496551
8.268962,57.505316
8.275379,57.50402
8.277397,57.497746
8.291554,57.493188
8.294536,57.489447
8.299475,57.487678
8.304424,57.484222
8.320982,57.462518
8.333654,57.45636
8.348271,57.453577
8.40202,57.429773
8.424824,57.425494
8.439114,57.417547
8.44551,57.416149
8.451899,57.416812
8.465979,57.421885
8.476807,57.41796
8.489466,57.400824
8.525696,57.381357
8.542728,57.377617
8.561725,57.366285
8.570072,57.365162
8.603993,57.355554
END
90,66,8.687958,57.525571
8.68832,57.524023
8.684382,57.525339
8.683412,57.529556
8.687023,57.528615
8.688834,57.529456
8.693764,57.529543
8.693087,57.524485
8.68832,57.524023
END




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