Longitude and Latitude Format

[Tim]

I have a excel spreadsheet in which longitude and latitude are
expressed by up to 6 digits after the decimal point.

When I import the spreadsheet into MapInfor (8.5) I say that the long/
lat columns are to be "float type".

When I look at the point data for that site within MapInfo there are
only up to 4 digits after the decimal point.

I need the resultant map to be as accurate as possible.

When is MapInfo truncating the long/lat coordinates?

What am I doing wrong?

Thanks!

Tim Ericson

[Hankins, Michael D.]

Change the type to decimal, 12,6. You can do this when you import the data into MapInfo.

Mike

[Uffe Kousgaard]

> When I look at the point data for that site within MapInfo there are
> only up to 4 digits after the decimal point.

All the digits are still there, but only some of them are shown to you.

Regards
Uffe Kousgaard

[David R Sherrod]

Tim, it's an "Advice to Users" sort of thing.  As Uffe stated, all the precision is maintained, you just don't see it in a browser window.  The precision is maintained when the table is exported (or translated) to other formats, too.

But you may have reasons to want to recover the data as an ascII file in the future---in which case you should follow Mike's advice and format the columns.  Examples of such need might be if you're going to the field and you want to have a printout of your lat/long data so that you and your handheld GPS receiver can home in on specific points, such as benchmarks or field stations or peculiar topographic features that have all the hallmarks of being gold depocenters.

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mapi...@googlegroups.com wrote on 10/09/2009 12:07:10 PM:

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> [MI-L] Re: Longitude and Latitude Format
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> Uffe Kousgaard
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> to:
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> mapinfo-l
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> 10/09/2009 12:07 PM
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> Sent by:
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> mapi...@googlegroups.com
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> Please respond to mapinfo-l

[Tim]

Thank you, Michael, Uffe and David!!

Tim

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[Eric Blasenheim]

Given that you will probably not be editing or expanding the data in
Pro, David's suggestions are valid. Just note that if for some reason
you had any data that you define as Decimal 12,6 you WILL get true
truncation if you were to do some math or editing that expanded the
data to more than 6 decimals. Or more than the limit to the left of
the decimal point. So using Decimal can be nice but has some dangers
in it.

As Uffe pointed out, float has the true precision but the browser does
not show it. As far as exporting as ASCII or any other format, one can
always do a SQL select where the column list contains expressions like
val(format$(ColumnName, "###.#########")) and the result will be
numbers formatted up to those number of decimals. The resulting query
table can be exported to text. So you can, with a little extra work,
get the best of both full precision and formatting when you need it.

Eric Blasenheim
PBBI (MapInfo)

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