Insufficient number of tie lines

Problem:

When performing a tie line search in TerraMatch, there are a number of reasons that the user might not see a sufficient number of tie lines after using the tie line search function. This is most likely due to settings not being proper for the dataset being considered. This article reviews potential settings for the user to tweak in order to get better (more) tie line results.

Note: There are also scenarios where the user would see no tie lines after running tie line search, which is reviewed in the following article: TerraMatch found “0 tie lines”.

Probable Resolution #1:

The dataset must have unique flight line numbers, which is required when processing multiple flights at once in Terra.

  • If processing True View 3DIS derived data, please view our True View Users Guide, Create True View Trajectories section. This reviews the location where the user can set trajectory numbering TV Evo.
  • If the user has LP360 or True View Evo, update the point source ID (flight number) used in LAS File Analyst to match the updated trajectory numbering.

Probable Resolution #2:

Alter the search tie line settings. If the surface is fairly flat with no distinct features, it’s possible that you won’t get proper xy tieline matching. On the other hand, if you don’t have the proper vertical relief, you would not see the xy error issues sufficiently to require this type of correction. You can try reducing the required slope for xy section line validity, but if the value is too small then the results would lose validity.

Regarding the finding of vertical tie lines, you may need to increase tie line length to get more valid vertical tie line matches for this type of area. Try increasing the define tie line length and depth settings and see if additional vertical tie lines are found.

It’s recommended to try using a tie line that is 3-5 times the nominal pulse spacing of the points getting to the ground. And a depth that will show 3-5 points from at least two lines when you draw a vertical section using the length and depth.

Probable Resolution #3:

Terra Match – Section line validity settings are not properly set for the type of flight be performed. The default TerraMatch setting will not work properly for True View 3DIS and other sUAS systems flown. Check your TMatch – Settings=>Tie Line settings dialog. For sUAS flights, xy>13 degrees and z<30 degrees is a good place to start.

Probable Resolution #4:

Ensure that the correct scanner system is being used. Setup your scanner system and make sure that it is being utilized in the the trajectory dialog before starting this process: Setting Scanner Systems. If using a True View 3DIS system, please reference the following scanner list: GeoCue 3DIS scanner systems list for Terrasolid: TerraMatch

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