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Week 1 - Introduction to ArcGIS and acquiring new data

Classroom topics:

  • Structure of the class.
  • Introduction to GIS
  • Applications in anthropology
  • Strengths, weaknesses, and critiques
  • Topics we will cover in this 10 week course

In Class Lab -- Week 1

Part I - Create a shapefile and digitize from a satellite image.

In this exercise we will learn how to create a polygon shapefile by digitizing the polygon from an satellite image of the pyramids of Giza.

  1. We will begin by downloading files from the class download directory. Download Giza_image.zip and pyramids.zip.
  2. Go to ArcCatalog and create a folder called "Giza". In that folder, create a polygon shapefile with one Text string attribute field called 'Title'.
  3. Unzip and add the "Giza_image" jpeg to an Arcmap project.
  4. Digitize two of the pyramids as polygons by starting an edit session. Once you have drawn them, open the attribute table and name these pyramids "Pyramid 1" and "2" in the Title Field. Change the symbology to hollow red shapes and label the shapes using the Title field.
  5. You've just done "heads up digitizing" on a satellite image.

 

Part II - How to import point locations from an XY table.

  1. In Part I you downloaded a CSV file called Pyramids.csv. These are data I got from a GoogleEarth blog site showing the locations of many pyramids in Egypt and a few in the Americas. Double-click the table file in Windows so you can view it in Excel. Note that the first line, which become field headings, consist of simple and short words. The table was Comma-delimited format (.CSV = comma-separated variables).
  2. Import the CSV file into Arcmap using the "Add XY..." command. As you saw, there is the Name column, and then coordinates in Latitude and Longitude and decimal degrees. Which column of values do you think goes in the X column and which goes in Y? Make sure that the data is assigned to the Geographic "WGS1984" coordinate system.
  3. The file is imported as an "event theme". You should see the points fall right where the pyramids that we digitized are located. If the new points don't fall within the polygons you digitized then there's a problem... maybe you needed to import Longitude as the X value and Latitude as the Y value?
  4. We want to convert these data to a regular point Shapefile. Make sure no features are selected, and then right click the layer and choose "Export Data..." to convert these data to shapefile. Remove the original Events layer from the Table of Contents. Load the new data into your view (and remove the Events theme). Label these points by right-clicking the new Shapefile data layer in Arcmap and choosing "Label features".

You just brought in raw point data from an XY text table. This is a very powerful technique for importing raw data tables from books, data sets online, and a variety of input tools like GPS units, total stations, laser transits.

Part III - In which countries are these pyramids found?

  1. To answer this question we need to download some reference datasets. Go to this data folder http://www.mapaspects.org/gis/data/ and go to /vectors/world/ and download "Admin_boundaries2004.zip" to your work space. These are data showing National and State (Provincial) level regions in a WGS1984, Decimal Degree reference system.
  2. Unzip and this folder and add these data to your view. Drag the Admin layer to the bottom of the Table of Contents so that these large polygons don't obscure the other layers.
  3. By using a spatial join we can have the attributes of the Admin layer appended to the Pyramids layer. Right click "Pyramids" shapefile point layer and go to Join... and then at the top of the Join box choose the box to Join using spatial location. Join to the Admin layer and call the output file "Pyramids_Admin".
  4. Open the attribute table of the resulting file. Note that the 38 rows of pyramid data now have Admin table data appended to the right. Scroll right to see these data. Sort the table by Country by right-clicking the CNTRY_NAME field and choosing Sort Ascending.
  5. How many pyramids are in each Administrative area? This question is answered easily by right-clicking the ADMIN_NAME field title and choosing "Summarize...". At the bottom of the dialog name the file "Admin_Pyramids_Table". The output appears in your table of contents. There should be four rows (admin areas with pyramids) and the COUNT of pyramids in each zone. Here we found that using generic administrative data can be useful in a number of ways.
  • you can use it to visually confirm that your data lines up with other "objective" data from other sources.
  • you can use it to compare your own datasets with familiar administrative categories for reports and other summary functions.

As you can see a powerful part of GIS is the ability to combine tabular data with geographical location. The Spatial Join function is very useful for combining datasets that are not otherwise compatible because they use different indexing systems or naming conventions, or they are in different languages. The common reference of spatial position brings them together.