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Gis--for Free!

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xm39hnu

Senior Member
Joined
Jul 10, 2003
Professional Status
General Public
State
Florida
This is a highly capapble GIS system which is file-compatible with ArcInfo, ArcView, etc. You can do 3-d maps, rotate them, overlay a tax map on them, shade your subject tract, view it in 3-D from altitude. It's name is GRASS, which is a government acronym for Geographic Resources Analysis Support System. There are free versions for Mac, Linux, and WinTel machines.

There are free maps available from USGS for most areas of the country. (Except mine. TVA controls the maps for Tennessee, and they charge $100 for a bunch of quadrangle charts on CD.) The map data which you can plot (including D-FIRMs, which are available from FEMA on CD; census data from census.gov) is extensive. Much of it is free, but a lot of satellite data has to be bought, if you need it.

Fair warning: There are over 300 separate programs in this package, and each does something different. The learning curve goes straight up, and it's greased. The potential uses for appraisal purposes is limited only by your capacity to learn a complex and versatile mapping system. You'll spend a lot of time learning how to do stuff.

Here's the link: http://grass.baylor.edu//index.html

For Mac users, try the Aqua version for OS X from http://www.openosx.org. They also have a textbook entitled "Open Source GIS: A Grass GIS Approach" which is an excellent tutorial on how to use the program for most anything. Kinda pricey at $125, but the payoff can be big. These guys have got a CD with all the support programs you need to run this on a Mac under OSX. The CD is $60, and you'll want the book too. The CD is great. Just plug it in, hit the installer, and you're ready to rock.

On the Baylor link, you'll find other links to several tutorials.

Enjoy
Jim
 

EDWARD BERRY

Senior Member
Joined
Jan 15, 2002
Professional Status
Certified General Appraiser
State
Arkansas
WONDERFUL,

HAVE you used any of it?

If so how?

In the backwoods-ed
 

xm39hnu

Senior Member
Joined
Jul 10, 2003
Professional Status
General Public
State
Florida
So far, I've used only the tutorial files (Spearfish). Mapped contours, roads, rivers, railroads, bug sites, and archeological sites. Sampled and mapped a portion of the dataset. Done the 3-D elevated view, rotated, exaggerated the elevation. Printed the results to both paper and PDF successfully.

This thing's a bear to learn, and I'm no lightweight where technology is concerned. Problem is, the functions are scattered all over the place. Over 300 separate programs. You don't have to separately learn all of them, but some of the significant ones are drast (display raster image), dvec (display vector image), nViz (3-D viewer), the functions which establish a new dataset; those which link new map information to a dataset -- ok, that's enough to play with for a month of free time.

My little rural portion of the world does not yet have georeferenced assessor's records. The state is pushing for it, but so far only about 13 out of 90 counties have undertaken georeferencing. Right now, all I'll be able to do with it is overlay the tax maps. That alone is worth the effort. Picture this: with the tax map overlaid on a quad chart, you can color in your subject parcel. You can search the map database and plot each parcel within your defined neighborhood with a color indicating the assessed value of improvements. Price range low, high, and predominant are now visible[/V]. Next, do it again with the actual year built of the principal improvement. Same picture: visible display of market data. But the ding-dang parcel info isn't georeferenced. I'll have to manually construct the database if I want it before the state gets there.

Some handier, more immediate uses come to mind. Riverfront or lakefront property can be shown platted on the quad chart, 3-D'd, and shown from an elevated view. This will give the user of the report visual information on the placement of the tract and its improvements. Flood map info from the D-FIRMs can be overlaid as well. (D-FIRM info is available in ArcView format, which GRASS can read directly.) Georeferencing a single tract is not so difficult as to be impractical, especially on special-case, hard-to-finance properties like custom resort homes. You can pull approximate points off the tax map, which, while they ain't exact, are accurate enough for this purpose.

My advice is to download it, get the Spearfish dataset, and start playing around with it. Hardest part is going to be learning what goes into those datasets so you can make use of publicly available data from FEMA and Census. There's a lot available from HUD, too, which is specially georeferenced for use in GIS systems. The potential of this program (not to menition that it's free) makes the time investment worth it. I plan to offer this mapping as an extra consulting service when I get it up an running. Till then, it's a time-consuming (but fascinating) toy.

Just to show you some of the income potential, let me relate this story: A recent client, a small town, wanted to put in a sewage system. They hired a consultant. The consultant told'em they'd need appraisals on easments across the private property of those who resisted the project, and we got called in. Easy money, once we learned about the Uniform Act requirements. But the project required a detailed map of the current city limits, with flood map information overlaid. The consultants hired an engineering firm, which charged them $750 for a D-sized map that a kid with a good box of crayons could've done better. Now they need one showing the gas lines, water lines, and buried cables. All this stuff is a piece of cake for GIS. (And Hewlett-Packard is now marketing a D-size inkjet printer for less than $1000). One assignment such as this would pay for the printer. Other possible uses: Zoning maps, subdivision maps, population density maps, -- the list is endless.

This thing will even answer such questions as, "If a freight train carrying five carloads of methylene chloride overturns in this bend right here, and each car carries 10,000 gallons, how many and which homes will have to be evacuated, and how much time do we have to do it." You can produce a movie showing the spread of the contaminant and how it will progress over time. (There's a tutorial on this, but I'm still in the basic stuff.)

As the commercial went, "Try it. You'll like it."
 
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