Question

clip a DTM using a not round boundary but export to rounded points

T

Dear all,

 

 

i have the following problem:

 

 

Using a DGN file i get different informations:

 

- DTM points

 

- Breaklines

 

- a perimeter

 

 

what I do:

 

- interpolate / generate a DTM 

 

- clip this DTM using the boundary

 

 

Result:

 

What I get: 

 

- A XYZ file or ASCII grid where the coordinates are not rounded to the full meter (e.g. 423545.455).

 

This is caused by the perimeter which is not rounded to full meters

 

 

What I need:

 

- The result should be a DTM with coordinated at the full metere, e.g. 423545.000

 

 

Is there any solution to tell FME that i want to export the DTM in a way that each DTM cell should be on straight coordintes?

 

 

Thanks for the help!

 

Thomas

10 replies

fmelizard
Rank
Userlevel 4
Badge +13
Hi,

 

 

If it is as you say:caused by the perimeter that is not rounded, have you tried rounding the perimeter before clipping?

 

 

Itay
T
Thanks Itay, for the quick reply.

 

 

This would be an option. Since i'm fairly new in FME could you give me please a hint how i could round a perimter which is a closed unregulary shaped polygon.

 

 

But still the possibility to tell FME that it should export grid cells on straight meters should not be so difficult. I would rather say that this is required very ofter from the user (who wants to work with raster data on x.34054 and such stuff) :-) .

 

 

Thomas
fmelizard
Rank
Userlevel 4
Badge +13
Hi Thomas,

 

 

In that case I think the RasterCellValueRounder is what you are searching for.

 

 

Itay
T
Dear Itay,

 

 

I think we have a small missunderstanding.

 

The content of the RasterCell represents the height of the DTM cell. This value can be whatever (not rounded) thats fully OK.

 

What i need is the coordinates of the cell (X and Y) are on staight meters, this means .000.

 

This can not be done by a simply rounding of the X and Y coordinates, since with a difference in this lateral coordinates i would have different height values in Z.

 

 

best regards

 

Thomas
fmelizard
Rank
Userlevel 4
Badge +13
Hi Thomas,

 

 

That makes sense, why would you want to round the cell values....

 

Anyway, You can coerce the raster into polygons and round off the coordinates, but that is where my line of thought ends.....

 

 

Itay
T
Thanks Itay,

 

 

i will look into the problem again.

 

 

But I'm still surpriced that its so difficult to tell FME to export a DTM on straight coordinates.

 

 

Have a nice day!

 

Thomas
takashi
Rank
Userlevel 2
Badge +17
Hi,

 

 

If you are using the NumricRasterizer to transform the DTM points to a raster, I think you can specify cell sizes (X / Y Cell Spacing) and ground extents (Minimum X / Y, Maximum X / Y) by rounded values. You can also use the AttributeRounder to round numeric attribute values, if necessary.

 

 

Takashi
fmelizard
Rank
Userlevel 4
Badge +13
Yes, it this option is also available in the SurfaceModeller, Thomas, which transformer are you using to create the DTM?

 

 

Itay
G
Badge +3
U could greate a 2Dgrid overlayed on the perimeter and use this to capture

 

the heights to integer coordinates.

 

U will have to rasterize your DTM and then resample the raster to get DTM-heights wich are on those integercoordinates.

 

 

I assume that the DTM points are not all on exact integer coordinates to start with (?)
T
Thank you Gio,

 

 

this is exactly what I thought could be the solution.

 

 

The problem is, that I'm very new at FME and i can not find the correct Transformers:

 

- Generate a Grid on certain coordinates

 

- fill this grid with interpolated heights from the original DTM

 

 

If you could give me please a transformer name or another hint would be heighly appriciated.

 

 

Thanks 

 

Thomas

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