SO432 Lab 5

SO432, GIS Fall 2008

Vertical Datums

You are to investigate whether the vertical datum (NAGD1927 or NAVD1988) will make a significant difference for tidal zone operations in Puget Sound.

This will be due next Tuesday during lab. You will also email the instructor the three DBF files you created.

Requirements:

This lab is entirely individual effort. You will not get any assistance from your classmates. If you need help, contact the instructor.
You are to create three DBF files with three fields: LAT, LONG, and Z for the difference (1) between MLLW and NGVD1929, (2) between MLLW and NAVD1988 , and (3) between NGVD 1929 and NAVD 1988 for your assigned DEM.
You are to create a quality map:
- With neat lines and a scale bar.
- With roads and streams overlaid from the correct TIGER file.
- With the water depths filled in from the NOAA esutarine bathymetry.
You are to plot and color code three map overlays showing the differences between the datums and attach these maps with your discussion.
You are to write a discussion on:
- why users of maps and nautical charts would want to care about the difference between the two datums in the area. Use specific numbers from you results to defend your answer.
- Did you create a raster or vector data set? Could this data have been turned into the other type, and would there be any advantage to having the data in the type?

Download:

The DEM you are assigned, from http://rocky.ess.washington.edu/data/raster/tenmeter/byquad/seattle/index.html
Get the NOAA bathymetry for the Puget Sound, from http://estuarinebathymetry.noaa.gov/
http://nauticalcharts.noaa.gov/csdl/vdatum.htm and then uncompress. Insure that you get the file for this area. Your computer also need the Java Runtime Environment installed. If VDATUM will not run, get Java from http://www.java.com/en/download/manual.jsp
If you do this exercise at home, you must insure that you have the latest MICRODEM and its help file from http://www.usna.edu/Users/oceano/pguth/website/microdemdown.htm.
If you do this exercise in the lab, insure that you have updated the computer to get the latest versions

The help file for MICRODEM has step by step directions under Tutorials in the Table of Contents, and a worked example.

Create an ASCII grid with lat/long values and with about 100 m spacing (you must convert this to degrees).
Use VDATUM to find the difference between the vertical datums.

References:

DEMs are assigned below.