Tuesday, May 12, 2015

A New User's Experience with NHDPlus & Tips for Other New Users

Recently, I got interested in National Hydrography Dataset (NHD), which includes hydrological data for the United States, for my research:  http://www.horizon-systems.com/NHDPlus/index.php

As stated in the `NHDPlus Version 2: User Guide (Data Model Version 2.1)`:

`NHDPlus is an integrated suite of application-ready geospatial data products, incorporating many of the best features of the National Hydrography Dataset (NHD), the National Elevation Dataset (NED), and the National Watershed Boundary Dataset (WBD).`

As a new user, I wanted to make best use of the training materials provided for NHDPlus Version 2. Therefore, I started doing the following exercises. An ArcGIS license is a pre-requisite to perform the exercises. I have a license for ArcGIS 10.2.1 for Desktop.

Exercise 0-Installing Tools and Data: Completed without any problem.

Exercise 1-Setting Up the Data:  

Part 1-Building Indexes and Raster Pyramids: I ran into a problem when I tried to launch `Prep NHDPlus V2.1 Data` tool in ArcCatalog. The error message was as follows:

updateParameters Syntax Error: Runtime error Traceback (most recent call last): File "D:\GIS\USA\NHDPlus V2\NHDPlusV21Tools\NHDPlusV21Toolbox\NHDPlusV2.1 Toolbox.tbx#PrepNHDPlusV21Data_NHDPlus21Tools.UpdateParameters.py", line 1, in File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\__init__.py", line 24, in from arcpy.toolbox import * File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\toolbox.py", line 356, in from management import Graph, GraphTemplate File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\management.py", line 22, in import _management File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\_management.py", line 14, in import _graph File "c:\program files (x86)\arcgis\desktop10.2\arcpy\arcpy\_graph.py", line 27, in import numpy ImportError: No module named numpy

I contacted NHDPlus support team regarding the error and I was told that the problem stemmed from NumPy. I uninstalled Python27 directory installed during ArcGIS installation and re-installed Python. The error message disappeared after I rebooted my computer.

Part 2-Relates & Joins:  I skipped this part.

Part 3-Updating NHDPlus V2.1 Data Components: I executed `Check NHDPlus V2.1 Currentness` tool. Despite the fact that ArcCatalog got busy and became non-responsive for a while, the tool was executed successfully.

Exercise 2-Linking Data to the NHD: 

Some background information about `linear referencing` is required for this exercise. I found the following online ArcGIS guide book which gives linear referencing information.

I completed this exercise without running into any problems.

Exercise 3-Navigating NHD with Geometry: 

I completed this exercise without any problems.

Exercise 4-Navigating NHD with NHDPlus Flow Table:

I completed this exercise without any problems.

I completed this exercise without any problems.

Exercise 6-Using the NHDPlus Raster Data Sets:

I completed this exercise without any problems.

Exercise 7-Watershed Delineation Using ArcGIS Spatial Analyst:

Steps 4-6: If more than one point is inadvertently created and added into the shapefile, the resulting watershed turns out very small as compared to the watershed shown in the document. I made this mistake and had to delete the extra point from the shapefile to obtain the watershed described in the document.

Exercise 8-NHDPlusV2 Simple Model:

Page 12-13: Details of the `concentration map` were not given. I created the `concentration map` by joining NHDFlowline.shp attribute table with the model output table. The joining was based on comid field.

This blog post will be updated as I progress with the NHDPlus exercises.

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