General Category => Using SLAMM => Topic started by: azarcos on January 31, 2020, 02:25:34 AM

Title: DEM setup
Post by: azarcos on January 31, 2020, 02:25:34 AM

I am new with this software. I want to setup a model for portugal. I have Lidar data for the baseline DEM, but I'm not certain about how to input this data into SLAMM . Could you provide a step by step overview?

My DEM is an ascii file (x,y,z) with a local coordinate system ETRS89:TM06 Portugal. I need to change this coordinate system to NAVD88? how to input coordinates in squared arranged grid? In the manual it  says that the "The model does not require NAVD88 data specifically, just that data be converted to an MTL basis. The user can either convert to a MTL basis prior to importing the data to SLAMM and set the "MTL-NAVD88" correction to zero, or use the other datum and interpret the "MTL-NAVD88" parameter to mean "MTL minus other datum." how to compute MTL-NAVD88 correction to zero?
Is there any tutorial to setup a model?

thanks a lot for your help!
Title: Re: DEM setup
Post by: Jonathan S. Clough on February 03, 2020, 08:55:41 AM
It has been a while since we have done any in-depth user training or tutorials.  Here is one done in Mexico in 2013.  These materials may be useful to you:

I believe that you are specifying a horizontal datum for your data.  What is the vertical datum of your elevations?  That is what must be converted to a MTL basis in some manner.

Best regards! -- Jonathan
Title: Re: DEM setup
Post by: azarcos on February 06, 2020, 09:26:35 AM
Thanks Jonathan, I will look to the materials.
The vertical datum is the mean sea level.

Title: Re: DEM setup
Post by: Jonathan S. Clough on February 07, 2020, 08:18:49 AM
Absent other information you can make the assumption that MSL (the average of continuous measurements or an inferred continuous curve) = MTL (the midpoint between MHHW and MLLW).

Therefore you can leave the MTL-NAVD88 parameter at zero.

Do pay attention to the vertical accuracy of your elevation data as that is an important consideration (is the data set precise enough to model the impacts of incremental changes in SLR?)

Good luck!