Hi Ben,
I guess you problem here might be the fact that some ( or rather a lot ) of
your records have been selected more than once, and therefore the entire
length
of all the lines will double, triple or more.
Try the following:
Select LineName, sphericalobjectlen(t_name.obj, "mi") From MyLineTab
Where obj Intersects any (Select obj from MyRegionTab
where Name = "TheRightName")
Group By LineName
Into MyNewSelection NoSelect
In this way every entry will only be shown ones. Of course the LineName
column
should be unique, eventually add a new column and update it with the RowID.
Do also have in mind that when you do a gruoping your obj is lost,
therefore you
have to select the Lenght information from the beginning.
I hope this helps
Peter
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Ben Humphrey wrote:
Okay, here's something COMPLETELY messed up.
I am conducting some length calculations on some line data for the US
railroad network. I did a select objects from the railroad table that
intersect another table of polygons. I save that as a table. I then do a
select sphericalobjectlen(t_name.obj, "mi") into sometable, calculate
statistics, and get a the sum, for each row in the original table selection
of line lengths. If I do it that way, I get over 6000 miles (which is way
off if you just look at the selection in a map window. If I combine all
line objects into one, and then double click on the single object, I get a
line length of only 1000, which seems much more reasonable. Anybody have
this experience before or am I using the wrong mapinfo commands?
Thanks
Ben
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