Tim,
You can use the areaoverlap function in an sql function if you just want a
text report of the data, Else you could create a result layer to get the
answers from by:
First copy New_SS_Thickness_Regions as a result layer, and have a map of
both it and the Depth_to_Brown_Zone_Regions layer.
Second, make the New_SS_Thickness_Regionslayer editable, select all and set
target
Select all from the Depth_to_Brown_Zone_Regions layer
Use Object Split and leave all the data as it was
Use a selection between the results layer and Depth_to_Brown_Zone_Regions
where Depth_to_Brown_Zone_Regions.obj contains results.obj, and you will get
all the data from both layers.
I think there is a Mapbasic routine around that does this process
automatically, but I think this is essentially the way that Arc would do it
as well (although it would be disguised as a intersect command).
-----Original Message-----
From: [EMAIL PROTECTED]
[mailto:[EMAIL PROTECTED]]On Behalf Of Tim Warman
Sent: Thursday, 19 July 2001 3:37 AM
To: Mapinfo-L
Subject: RE: MI-L Overlap function
RE: MI-L Overlap functionThat's what I thought too, but it doesn't return
the areas of overlap, it returns the entire object in layer 2. Is this some
sort of bug or am I missing something?
Also, the reason I can't use the object>split function is that the original
example I gave is actually a simplified version of the actual problem I'm
trying to solve.
I started out with two sets of contours. Table A had contours of the
cumulative thickness of sand bodies in a particular formation. Table B had
contours of the depth below ground surface to a marker bed within the same
formation. From these contour maps I created a series of regions bounded by
successive contours (e.g.. the area between the 800 and 1000 ft contours was
now a regions with an average value of 900 ft).
What I'm trying to do is find the area where the cumulative sand thickness
is >=800 ft AND the depth to the marker bed is >=800 ft. I tried the query:
Select overlap(Depth_to_Brown_Zone_Regions.obj,
New_SS_Thickness_Regions.obj) from Depth_to_Brown_Zone_Regions,
New_SS_Thickness_Regions where Depth_to_Brown_Zone_Regions.obj intersects
New_SS_Thickness_Regions.obj into Selection
but as in the simplified version of the problem the query seems to ignore
the Overlap request and only returns the results to the Where part of the
query.
This is exactly the sort of problem that GIS was designed to solve in the
first place, so I'm sure there's a way to do it.
TIA
_____________________________
Tim Warman
Groundwater Geologist/GIS Guy
Richard C. Slade & Associates LLC
North Hollywood, CA, USA
+1 (818) 506 0418
-----Original Message-----
From: Windeler, David [mailto:[EMAIL PROTECTED]]
Sent: Wednesday, July 18, 2001 5:40 AM
To: 'Tim Warman'
Subject: RE: MI-L Overlap function
Running an SQL select as you did will produce areas of overlap where the
two objects intersect. This could be a problem as a polyline may only
intersect once with a polygon. An alternative approach is to ensure that
there is an identical data column in both tables and then perform the SQL
select where col_name1 = col_name2. This is similar to the Objects Erase
statement. Hopefully this will help you out.
-----Original Message-----
From: Tim Warman [mailto:[EMAIL PROTECTED]]
Sent: Tuesday, July 17, 2001 10:03 PM
To: Mapinfo-L
Subject: MI-L Overlap function
Listers,
I'm having trouble getting the Overlap function to work properly (i.e. the
way I want it to) through the SQL dialogue box.
I have two regions in separate tables which partially overlap. I want to
create a new object that represents just this overlap area.
I run a query using the SQL dialogue box which when viewed in the MapBasic
window looks like this:
Select Overlap(Layer_2.obj, Layer_1.obj) from Layer_2, Layer_1 where
Layer_2.Obj intersects Layer_1.Obj into Selection
Unfortunately this just selects the entire object in Layer_2.
It's obvious I don't quite understand how the Overlap function works, but
it's not well documented in the MapBasic help, and not documented at all
in
the MI help.
Can anyone point me in the right direction?
TIA,
_____________________________
Tim Warman
Groundwater Geologist/GIS Guy
Richard C. Slade & Associates LLC
North Hollywood, CA, USA
+1 (818) 506 0418
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