Cultural and Bathymetric Data

Owned by Erlend Kvinnesland
Last updated: Oct 10, 2011 by Former user (Deleted)Version comment
5 min read

Introduction

The exercises require a training dataset that will be distributed and used in courses. Otherwise one can download it from Tutorial data1 .

Exercises

Import Data

The global coastline is public domain data and can be downloaded in different resolutions from NGDCs webpage: http://www.ngdc.noaa.gov/mgg/shorelines/gshhs.html.

Exercise

Import coastline

  1. Right-click the Cultural Data folder and select Import > Generic
  2. Click the browse button and select the gshhs_f.b file from ...\inbox\01coastline
  3. Tick the Specify import area box and click the Area of Interest tab.
  4. Enter the following range:
  5. Click Execute
  6. When prompted with the Select Datum and Coordinate system dialog, select:
  7. Click OK

A note on Geodesy

When assembling data into a project from different sources, it is not uncommon that the data are in different datum and projections. For the data types that are to be loaded into this demo project this is the case, some data being in UTM51S, some in UTM52S, and some in geodetic coordinates (latitude and longitude). A Geocap project has no restrictions on how the user chooses to store the data. Therefore, the data can be loaded and kept with their input geodetic settings. However in order to visualize and work efficiently with the data, it is necessary that the data is converted to the same projection/datum. This can be done in 2 ways:

  1. The dataset in the project is replaced with the converted data
  2. The original is not replaced, but a converted copy is made

It is important to be tidy when dealing with geodetic properties. A Geocap project has no restrictions, and whilst this gives the user lots of freedom and flexibility, it also makes it possible for the user to “get into a muddle” with the data regarding their geodetic properties. It is therefore recommended that if the user decides to keep data from more than 1 projection in a Geocap project, he/she names the data so that he/she easily can see which geodetic properties the dataset has, e.g.

Alternatively, the user can group the data into subfolders where the folder name shows what projection the data is in.

In the demo project we now are going to construct, all the data shall be converted to UTM Zone 51S with the datum WGS84.

Exercise

Convert coastline to UTM 51S

  1. Right click the GSHHS coastline and select All commands > Shared commands > Operations > Convert to UTM... or alternatively find the command in the Toolbox
  2. Set the datum to World Geodetic System 1984 and the coordinate system to UTM zone 51 and hemisphere S.
  3. Use the Replace input option (the original geodetic coastline is lost after the conversion).
  4. Click Execute

Geocap supports a vast amounts of polygon formats such as KML, Shapefiles etc.

Exercise

Import fields and licenses

  1. If these data are not present in the training dataset create them artificially by digitizing them with Tools -> Quick Digitizing. Create the folders as described below and place the fields and licenses correctly.
  1. Right-click the Cultural Data folder and select Import > Generic
  2. Click the browse button and select the fields.shp file from \inbox\01CulturalData\fields
  3. Click Execute
  4. Click the browse button again and select the Licenses.kml file from \inbox\01CulturalData\licenses
  5. Click Execute

Notice that Geocap automatically recognize the datum and coordinate system from shapefiles and KML-files.

Remember to convert the fields and licenses to UTM 51S

ETOPO1 is a 1 arc-minute global grid relief model of Earth's surface that integrates land topography and ocean bathymetry. You can download the whole or parts of the grid from NOAAs website: http://www.ngdc.noaa.gov/mgg/global/global.html

Exercise

Import etopo1 relief grid

  1. Create a new folder called Relief Grid
  2. Right-click the Relief Grid folder and select Import > Generic.
  3. Click the browse button and select the etopo1_aus.g98 file from \inbox\02etopo1.
  4. You don't need to use Specify import area because the dataset is already cropped correctly.
  5. Click the Reader Options tab and tick the Invert Z box because the grid has negative values for sea depths, and positive values for heights above sea level. Usually bathymetry data has positive values for depths.
  6. Click Execute

Remember to convert the grid to UTM 51S

Exercise

Set grids schema to Seabed Surface

  1. Right-click the etopo1_aus grid and select Set Schema > Seabed Surface

Notice that the dataset icon changed and that you now have several other commands available in the right-click menu.

Display Data

When displaying data in Geocap is important to scale the graphics window correctly. You can scale the window to a specific dataset or to all datasets in a folder. This is done by right-clicking a dataset or folder and selecting Zoom to Data/Folder. You can also scale the Z-axis by scrolling the wheel on the mouse.

Exercise

Try out different ways to display the seabed

Display

  1. Right-click etopo1_aus and select Display. The grid should now be displayed in one solid color.
  2. Click the icon to clear the graphics.

Map Data

  1. Right-click etopo1_aus and select Map Data. The grid has now been mapped on the full data range from -2974 (red) to 7238 (blue).
  2. Click the icon to clear the graphics.

The two previous methods does not distinguish between land and sea in a good way. Thus we are going to map land and sea in two different shades of color.

Map Land

  1. Right-click etopo1_aus and select Map Land. This maps everything above sea level in a shade from green to brown.
  2. Right-click etopo1_aus and select Map Sea. This maps everything below sea level in a blue shade.
  3. Click the icon to clear the graphics.

None of the previous methods will display the grid in full resolution as Geocap automatically decimates large datasets to make the display quicker. This is why we also have a LOD (level of detail) display command which adjust the resolution based on your zoom level.

LOD Grid Display

  1. Click etopo1_aus and double click the LOD Grid Display...* command in the Visualization folder under Shared commands in the Toolbox
  2. Demonstrate the effect of LOD by pressing W (wire mode) on your keyboard and zoom in an out. Notice that the squares get smaller as you zoom closer.
  3. Press S on your keyboard to go back to solid mode.
Exercise

Display cultural data

  1. Right-click GSHHS and select Display.
  2. Right-click fields and select Display.
  3. Right-click Licenses and select Display