October 16, 2019, 06:58:21 PM

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First calculate the longest term average elevation-change rate for your SET tables that you have available.

Then calculate the elevation of the SET table relative to MTL in "half-tide units."  As a reminder, half-tide units are "elevation-in-meters / (0.5 * GTU-in-meters )"

Then, plot these data on a graph so you can understand the relationship between SET elevation and measured elevation changes.   

A line using the accretion spreadsheet data can then be fit through the data to the best of your capability.

e.g. Fig 4 from https://www.sciencedirect.com/science/article/pii/S1364815216302705#fig4

Often SET tables are not set at elevations throughout the tidal range and are focused up around MHW so you would need to estimate the other portions of the range or use a model such as MEM3 to help fill out the relationship between marsh platform elevation and predicted accretion rates.

This is a quick birds-eye view of the procedure, please ask specific questions about the spreadsheet and we will answer them ASAP.

Love the user name BTW.

Regards!  - -Jonathan
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Model Formulation & Parameters / Specifying accretion as a func...
Last post by slammdunk - October 01, 2019, 04:19:42 AM
Hello Jonathon and Marco,

I am new to SLAMM and have had some difficulties understanding how to vary accretion rates as a function of cell elevation for different NWI wetland codes. I am hoping you can provide some more guidance on how to go about this.

I would like to use surface elevation change data from SETs that were placed in marsh and mangrove regions. Rather than breaking up the dataset for subsites around each SET, I would like to have accretion rates vary with elevation and tidal range for marsh and mangroves. I'm not certain about how to input this data into SLAMM though. Could you provide a step by step overview?

I have read through the user manual and technical guides, and have tried playing with the Excel SLAMM6_Accretion file included with the download. However, I'm still confused about how to go forward.  ???  Could you also provide an overview of the SLAMM6_Accretion file- bit of an introduction on how to utilize the spreadsheet?

Thank you ahead of time for all your help!   :)
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Using SLAMM / Re: Floating point error
Last post by andybell - September 19, 2019, 08:13:20 AM
Hi Johnathan,
thanks for the helpful reply.

Yes, the same 10m resolution data set works in 6.0 but not in 6.7
I tried the 2m resolution set in 6.0 and it went to write to disc then crashed...unsurprisingly; they are pretty big files.

I have ordered more memory for the laptop and will try the binary option for both datasets in 6.7 as you advise.

If this doesn't work I will zip up the 10m data for you to diagnose stepwise in 6.7, but that will be my last option knowing how busy you are.
All the best
Andy
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Using SLAMM / Re: MTL parameter for station ...
Last post by Jonathan S. Clough - September 18, 2019, 03:42:20 PM
The DEM must have some vertical datum to which elevations are referenced -- are the elevations in terms of the 1974 datum?

The MTL-NAVD88 parameter is set up such that if you looked at a gauge and there was a referenced MTL height and a referenced NAVD88 height, the value would be the difference of the two numbers referenced.

For example, at this station

MTL is 4.451 and NAVD88 is 3.134 meaning that MTL-NAVD88 would be approximately 1.3 meters.


NAVD88 can be substituted for whatever the datum of the elevation data set is.  So you can convert your datum of elevation to MTL (often ~MSL) and then set the MTL-NAVD88 parameter to zero.

In the case of your figure, if your elevation data are in 1974 datum, MTL-NAVD88 would be 1.46 meters.

Been traveling, sorry about the delay in response -- hope this helps.

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Using SLAMM / Re: Floating point error
Last post by Jonathan S. Clough - September 18, 2019, 03:31:02 PM
Hi.

The 64-bit version of the software should be able to accommodate nearly any map size -- the limitations are the memory of the machine (and there are also practical limitations in terms of how long it takes to load and run simulations.)   We have found the maximum size that is reasonably practicable to run is approximately 26 GB of memory (~250 million cells) but that obviously requires 32 GB of memory or more. 

Note the memory utilization in GB is given in the SLAMM File setup window and different optimization options are available a the bottom of the screen. 

e.g. "Cells to Track 7,169,539, memory utilization in GB 0.7478"

Are you saying that data can be input at 10m resolution in 6.0.1 but that 6.7 crashes with the same data set?  Have you tried converting the data to binary using the binary button?  This significantly optimizes input/output and may shed light on the problem.  If you cannot solve the problem, you can send me the data files and I can look at it, but I'm afraid I have not been very responsive in terms of loading other people's data lately.  Sorry that the software is not giving you a more helpful error message. 

I hope your problem resolves shortly.
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Using SLAMM / Re: Floating point error
Last post by andybell - September 18, 2019, 11:41:04 AM
Hi,
A further update.
The data works in version 6.0.1 at the 10m resolution level but runs out of memory at the 2m resolution.

It would nice to run 6.7 version to get the carbon module.

Kind regards
Andy
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Using SLAMM / Re: Floating point error
Last post by andybell - September 18, 2019, 05:44:06 AM
Hi
Just as an update; I used the sample data and the programme works fine. Therefore it is an issue with my data.
The *.ASC files check OK within SLAMM and they load without issue in QGIS and ArcGIS.

Can anyone advise what are the problems within data that might trigger the "Floating Point" error?

Much obliged
Andy
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Using SLAMM / Floating point error
Last post by andybell - September 17, 2019, 04:01:03 PM
Hi,
I have just installed SLAMM 6.7 on my laptop (8GB Ramm on windows 10)
I am trying to run a model that I have downscaled from 2m to 10m resolution, but get an error when it reaches 6% in reading the site characteristics. The error reads "Invalid Floating Point Operation". The error comes up when the 6% progress is met

Any clues what might cause this?
Many thanks in advance

Andy


9
Using SLAMM / MTL parameter for station in H...
Last post by felipe.costa@wwf.de - August 14, 2019, 09:04:18 AM
Hello,

I have been struggling to understand how to use the parameter MTL - NAVD88 and would like to check whether my assumptions are correct :)

I believe that since my topgraphic data (DEM) is not projected into any vertical datum, it would be enough to use a factor that would correct the DEM in terms of MTL, right?

If this is right, I would need to factor of correction which accounts for the Tide Mean Level minus the Local Datum level, right?

The station I am considering as input is the Tsim Bei Tsui (ID=1366), which provides the following diagram:
https://www.psmsl.org/data/obtaining/rlr.diagrams/1366.php ; (diagram attached to the message too).
You cannot see attachments on this board.

Is it correct that I should apply the paremeter as" MSL (2001-12) minus Local datum"? In this case, based on the diagram, I would have to use it equals 1.46m.

Can anyone please help me?

Best,
Felipe
10
Using SLAMM / Re: NWI
Last post by Jonathan S. Clough - August 12, 2019, 01:55:53 PM
NWI is a product of considerable technical expertise from US FWS that includes satellite data, infrared photography data, photographic interpretation, and considerable GIS expertise. 

https://www.fws.gov/wetlands/nwi/Overview.html

You do not need an NWI data set to use SLAMM however.  You do need some sort of high-quality vegetation land-cover polygons that can be cross-referenced to the SLAMM categories.

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