Friday, January 16, 2009

TR-55 Hydrologic Analysis with Map3D

This is still in draft...

TR-55 Analysis with Map3D


1) Download Soils GIS data


2) Look up hydrologic group data for the GIS soils data


3) Use the soil vlookup function in the CN Database.xls file to facilitate matching of hyd groups to soils types.  Will need to set up vlookup table in order to do search.


4) Open the dbf file of the Soils GIS data.  This lists the object data for the soils linework that will be imported in to the dwg.  Create a column in this file and add the hyd group data.  Make certain that the hyd group data matches up to the appropriate soils linework before proceding.


5) Using Map3D, import the shp file you just edited.  Adjust the dialog box settings so that the object data and linework comes in correctly.  Set the object data template so that the hyd group is included.


6) Prepare the linework for topology creation using map cleanup tools.  Create centroids for the linework and be sure to assign a correct block and the appropriate unique layer.  The layer assignments are crucial because you will need to do isolation commands with future steps.  


7)Another crucial step when creating topologies is that the topology linework must not be altered in anyway, shape, or form after creating the topology.  This will affect topology overlays that you will be performing once you prepare all the topologies correctly.  I place the linework on its own unique layer and then lock down said layer.


8)Create an annotative template for the soils topology.  This is a little tricky at first, but incredibly easy to master after a couple go arounds.  The template will be attached to the centroids of the topologys whose attributes you want annotated.


8)Now that the soils linework has been taken care of, and transformed into a map3d topology.


9)Create linework for the watersheds in the drawing.  Make sure that the linework of each watershed consists of line segments only.  Polygons will only be assigned to linework that forms a closed polygon, and an error message will be returned for errant linework that doesn’t form a closed polygon.


10) When creating the topology from the watershed linework, make certain to have MAP3D create centroids when the topology is formed (AND assign them to a unique layer).  Define the object data table for the watershed topology with the watershed name.  Assign the object data tables to the centroids just created.


11) Manually enter in the watershed names for the watershed topology.


12) Delineate the various land uses according the cover types listed in USDA Technical Release 55 - Urban Hydrology for Small Watersheds, pgs (2-5)-(2-8).  Create the linework  in a simlar fashion to how it was done in the soils and watershed topologys .


13) Create centroids for the linework when creating the landuse topology.  Create variables in the object data template for land use and condition and centroid id.  Assign the object data template for land use to the pertinent centroids.


14) Export the land use topology to an ESRI shp file.   A database file (.dbf) is created along with the shp file for storing the object data.  This table can be opened and edited in either excel or access.  The centroid id that was assigned for the land use object data table will become the go between for transferring data. 


15) Use the excel pulldown lists for selecting the land uses and condition.  Not doing so jeopardizes automated steps futher ahead because the land use nomenclature might not match up to its database lookup location.


16 )Arrange the data columns so that a copy and paste operation can be performed that will transfer the centroid id, land use, and condition between the excel worksheet and the dbf file.


17) Transfer the data from the land use and condition back to the dbf.


18) Reimport the just edited shp file.  (try…. Delete the line work from the previous topology prior to importing the shp file with updated database)



> Overlay the topologies


> Create object data tables for the overlay topology with attributes of each overlay (and the curve number (CN) and area for the final overlay)


> For final topology, export the topology to a shp file.  Go into the the dbf and grab the centroid id, land use, condition, and hydrologic group and copy to the CN Lookup tab of the CN database excel spreadsheet.  Make certain that all columns line up correctly and the vlookup function of column A will automatically assign a curve number for each centroid.  Copy this data back to the CN column so that each centroid id has been assigned a curve number.


> in order to assign annotate the attributes of the final topology, the exported shp file will need to be reimported into the drawing.