Core to the the development of distributed mapping systems over the internet is the concept of web services and the interoperability upon which they are based as the means of communication between systems. This week’s lecture and focuses on the core concepts of geospatial Services Oriented Architectures and the open interoperability standards from the Open Geospatial Consortium that enable the exchange of map images and data over the web.
Expected Outcomes
By the end of this class module you should understand the following:
The difference between raster and vector data formats and the utilities for retrieving information about supported file formats
The available resources for determining the projection parameters for different named coordinate reference systems and the command line tools for performing basic coordinate transformations
The three general tiers of a geospatial services oriented architecture and the components that may exist in those tiers
The key Open Geospatial Consortium standards for access, data, and representation
Key Concepts
Raster and Vector Data Models
Basic concepts of coordinate transformation and how the parameters that define a transformation may be used to perform basic coordinate transformation calculations using the cs2cs utility
The tiers of a geospatial services oriented architecture
The constituent components of SOA tiers
The role of OGC services in providing connectivity between SOA tiers
The OGC WMS, WFS, WCS, GML, and KML standards and their respective capabilities and purposes
Module 3 - GIS and Services Oriented Architectures
Geography 485/585L: Internet Mapping
Lab Assignment: Proj4, GDAL, and OGR
This week’s lab concentrates on some command line tools that are useful in working with raster and vector data sets. These tools should be available on your personal computers (through the installation of the FW-Tools package for Windows, or the GDAL, OGR, and Proj4 frameworks on the Mac) and are also available on the class server where you have been doing your homework assignments. If you would like to use the utility programs installed on the class server you will need to copy your downloaded files (using WinSCP [Windows], or Fugu [Mac}) from your local computer to the class server. You don’t have to put the files in your “public_html” directory, just your home directory or a separate folder will suffice.
As with the previous labs, submit your writeup as a web address for an HTML document linked to your class home page and accessible via the web.
Here are some useful links to documentation and information about the tools that you will be working with today.
Download three data products from one of the data download sites that you found in week 1 for the lab assignment. Make sure to download at least one vector and one raster data product as part of the set you download. If you need to go to different site(s) to download the data, feel free to do so.
Question 1
Briefly describe each dataset based upon the information from the web site.
Question 2
Examine each file using either gdalinfo or ogrinfo (depending upon whether it is a raster or vector data product), and answer the following questions about each data set:
What is the projection/coordinate system for the data product? If it is undefined, note it.
What is the spatial extent of the data product?
If it is a vector dataset, how many features does it have?
If it is a raster dataset, what is the pixel resolution (include units) of the dataset?
Question 3
Use proj or cs2cs (I suggest you use cs2cs) to calculate the coordinates of the spatial extent of the datasets that you downloaded in UTM Zone 13N, NAD27. Paste the input and output of the command(s) into your writeup.
