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Home - General / All posts - transform polygon to area and then calculate surface area
J. Dressel1 post(s)
#08-Sep-20 21:59

Hi,

getting started with Manifold 9 after having used Manifold 8 some 8 years ago....

something simple: how do I create areas from polygon lines?

second question: how do I get the surface area (e.g. in m2) of an area calculated?

Thanks heaps in advance!

Best regards, Joey

lionel

661 post(s)
#08-Sep-20 23:00

it a bit different with the new GUI but without RTFM i could succeed !!

1) polygon line ?

Polygon = area !!

join joined lines to create polygon ?

2) for area you need to use copy to create a new column name

the carret is in meter 100x100 so 10000 value is easy to calculate

regard's

Attachments:
MAnifold9_Transform-Area.map
MAnifold9_TRansform-Area.png


union

lionel

661 post(s)
#08-Sep-20 23:24

1) don't use a lot Manifold 9 but i think you have to use read documentation related to the function

GeomBoundedAreas(<geom>, <tolerance>): <table> at http://manifold.net/doc/mfd9/sql_functions.htm

In all manifold function , i don't really understand tolerance/precision range value even i understand that we must care about the projection relative to compute area or angle or distance with precision !!

regard's


union

dale

564 post(s)
#09-Sep-20 05:58

If Eight is what you know, then at the bare minimum watch the videos over on the Manifold Youtube channel.

Like this one Around 2:33 in answers one of your questions.

Nine is different to Eight. The video tutorials are really worth watching, and will give an idea of just where you might need to look to answer your questions. That's a minimum.

Dimitri


6,206 post(s)
#09-Sep-20 08:28

how do I create areas from polygon lines?

Easy. Use Trace. In the Transform Reference, see the Transform - Geometry: Trace topic.

how do I get the surface area (e.g. in m2) of an area calculated?

Easy. Use Copy : area. In the Transform Reference, see the Transform - Geometry: Copy topic. The area option is so simple it's not illustrated (I think it should be, and have sent in a suggestion), but here's how:

1. Open the drawing or the layer in the map that's got the areas of interest.

2. In the Transform pane, choose the drawing with the areas of interest (in the screenshots the drawing is named Areas), and choose the Geom field. Double-click Copy in the list of templates. That launches the template.

3. In the Copy template, choose area as the Use option, and choose whatever units of measure you want.

If the drawing is in lat/lon (for shame!) you get a choice of arc minutes, arc seconds, radians or degrees. If the drawing is in some sensible projection (yay!) that uses linear measures, you get an enormously long list of units you can choose. Choose meters, for example, and you get areas measured in square meters.

The Measure box, by the way, lets you choose either auto (native Euclidean for linear measure projections and geodetic for lat/lon) or geodetic, to always use Vincenty formulae over the ellipsoid.

4. In the Result box, give the name of a new field that will be created in the drawing's table into which the results will be saved. It pays to name it something memorable, like "areas in square meters" or whatever.

5. Press the Transform button.

What's definitely useful about the above is how easy it is to get units of measure in whatever you want, like in square feet or square miles even if the drawing's native unit of measure is meters.

Attachments:
get_area_measurement1.png
get_area_measurement2.png

adamw


9,415 post(s)
#09-Sep-20 10:12

A small correction: if the drawing is in lat/lon, the unit choices for area / length / etc, are still metric, the transform is going to use geodetic computations.

JoeyD2 post(s)
#12-Sep-20 10:53

Thanks, very helpful! The online manual is really comprehensive, but finding specific things is not always easy.

Dimitri


6,206 post(s)
#09-Sep-20 08:52

Forgot to say... You can also do this dynamically using a Computed Field (see the examples at the very end of the topic to get area), or another way to do it non-dynamically is to use an Expression in the transform pane.

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