grid based maps

Alex Thomas alex at DIDG.COM
Sat Oct 9 11:22:40 CDT 2004

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I did exactly this for 192 species.

I first decided the cell size of my grids and calculated how many columns
and rows of cells would be needed to cover my study area.

I then wrote a database routine in Access that for each species created a
species text file then in fixed steps working from top left corner I queried
whether a record for the species existed in the database that had a lat-long
which occurred within the cell. If there was a record I wrote a '0' and if
there was a record of kind A I wrote a '1', of type B a '2', etc. , and
worked down to the lower right cell.

I then created a base map in PICT format.

Using MacGIS (Hulse, D. and K. Larson (1992). MacGIS 2.0.1. Eugene,
University of Oregon.) I then combined the base map with the overlay by
importing the species text file, then exported the result to a PICT file.
MacGIS had a scripting capability so I only had to do about three clicks per
species, but I did have to manually process each species. 

I then laid the PICT files out using Adobe PageMaker, but it could just as
easily be done (now) in Word.

Hope this helps,


Alex Thomas
Didg Information Systems Pty Ltd
220 Gertrude Street
Fitzroy VIC 3065

Mb. 61-(0)417-490-594
Em. alex at

Professional applications and services for recording and brokering wildlife

-----Original Message-----
From: Taxacom Discussion List [mailto:TAXACOM at LISTSERV.NHM.KU.EDU] On Behalf
Of Torbjörn Tyler
Sent: Friday, 8 October 2004 23:39
Subject: [TAXACOM] grid based maps

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Concerning the endless problem with distribution visualization...

The new version of the mapping program iMap indeed appears very promising,
but still I have not found any program that can help me produce my
grid-based maps (not based on lat./longitude data or US zip-codes, which are
the formats handled by iMap). 

I want a system where I a can use any empty map, put any grid upon it,
assign a label to each grid square and then use the data in my database (in
the simpliest case containing presence/absence information for each taxon in
each labeled grid-square) to accordingly fill some of the squares with black
colour. I suppose it would be very simple to write such a program and I hope
someone has allready done it (preferably for Mac) but I have not been able
to find any such possibility in any of the mapping programs tested so far.
(In some programs it is possible to "cheat" the program by assigning a
coordinate to each grid and then try to choose a squarical symbol that fits
exactly in the sqare on my map but this is not very very handy and the maps
produced this way are never perfect ...).

Does anyone have a solution for this?


Torbjörn Tyler   /  Projekt Skånes Flora

Department of Ecology
Plant Ecology and Systematics
Ecology Building                                	
Sölvegatan 37         	
SE-223 62 Lund                          	
tel. +(0)46-222 09 10
fax + (0)46-222 44 23
e-mail: torbjorn.tyler at

Private address: Bredgatan 12B, SE-243 32 Höör (=Hoeoer), tel.

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