Terrain elevation data interfacing with simulink

[Mle]

Hello, I have used the standard blocks from simulink to interface with flight gear 3.4. Everything seems to work well, except that the received ground elevation is a constant 192. I am running the interface using the generated script. When running fg alone the elevation data is correct. Any idea how to solve this issue?

[jano]

Hi, you can check in flightgear property tree if "/position/ground-elev-m" is the same as what you receive in simulink, if yes the net_ctrl protocol should be working fine and the problem is in simulink making the plane flight at the same altitude , or a problem with the way this altitude is processed on external net fdm

i'm not sure it was the case for 3.4, but for a recent Fg the command line options to play with simulink when i gave a one month free try were:

Code: Select all

 --native-fdm=socket,in,30,,5503,udp
--fdm=null
--native-ctrls=socket,out,30,127.0.0.1,5505,udp

(using the net_fdm and net_ctrl blocks, the ports are to match your settings in simulink ..)

[Mle]

Hi thanks very much for your answer. I am still not quite sure I understand. I send to fg lat lon and alt data, and I see their effect on the altitude and position in fg. The property in fg gui is the same as the one received in simulink. I thought that the ground elevation should change regardless of the flying altitude (dependent only on lat lon data)

[jano]

I thought that the ground elevation should change regardless of the flying altitude (dependent only on lat lon data)

yep that's the case here, i didn't notice it was a ground elevation altitude it can be stuck at the same altitude if you're immobile, on a very flat land or if it take the altitude on a 3d model flying at the same altitude.
here the ground altitude change in FG for a ksfo landing in external fdm, with the latest FG version compatible with simulink net_fdm (2020.3) so i can't be of much help for your case, given both the net_fdm and net_ctrl procols seems to be working.
any reason you're still using FG 3.4 ?

[wkitty42]

it should also be noted that if anyone is running FG older than 2020.3.11 (the current Long Term Support [aka LTS] version), they should upgrade to the latest as older versions are no longer supported...

also, in the case of simulink, there may need to be some editing of the options used to start FG... especially with the newer version of FG... at least one option that i've seen used with simulink starting FG has been deprecated for a while and finally removed... what happens is that FG will not start when it sees an invalid option... the solution is to edit the bat file that simulink uses to start FG and remove the invalid option... then everything should work as it did in older versions of FG...