Using public mapservers

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Alex Brown

Although Internet access to maps and GIS data was an early application of web graphics, it's only recently that fully interactive maps of many kinds of municipal and state public data have become widely available on the Web, in addition to the Federal data that has been available for years. This can be a tremendous community planning resource as well as a tool for teaching, study, and research. In Massachusetts, our state-level GIS office, MassGIS (http://www.mass.gov/mgis) provides access to public GIS data, and many town and city GIS offices now find they can both offer public access to GIS data, and smooth operations within their offices, sometimes with significant savings. From the Town of Amherst GIS website (http://gis.amherstma.gov):

Mapservers differ significantly in the software technology used to provide their services. Like most other areas of networking technology, GIS web mapservers have been drawn into standardization by the needs of users for compatibility and flexibility. The industry organization most closely connected with this effort is Open Geospatial Consortium (OGC) (http://www.opengeospatial.org), but the most influential aspect of the effort is a growing body of successful Open Source software implementing these standards. The software development community for Open Source, Open Geospatial Consortium mapservers and similar applications, has grown to many hundreds of developers, some in government and industry as well as academia. Applications are often highly specialized and technical, but Open Source mapservers have found an important role in municipal GIS service delivery -- for examples, see http://mapsonline.net. One of the most important features of OGC standard mapservers is the ability to combine data layers from more than one server, for visualization and analysis. GIS software compatible with these mapservers can also combine mapserver data and local databases and files. For a discussion of standardization and open source in mapservers for public GIS see Open Source public mapservers.

ESRI, the dominant vendor of GIS software, provides a collection of "Internet Map Server (IMS)" software tools with the product name "ArcIMS". Although installation and configuration of ArcIMS can be difficult, the completed ArcIMS system makes it trivial to compose an interactive map service with several layers, and make it available as a web page. This makes it possible for less skilled GIS staff to post new and revised GIS data. ESRI ArcIMS mapserver web sites are generally not compatible with OGC standard mapservers; instead of the potential for combination of OGC standard mapserver layers described above, ESRI products generally offer combination of ESRI ArcIMS mapserver data layers and local data sources. Because government agencies often provide mapserver access to public data using ESRI ArcIMS, this is less of a limitation than it might seem at first.


We will look at different ways to use two public mapservers:

using three different types of software:

  • web browser
  • free GIS viewer (ESRI AEJEE)
  • GIS workstation (ESRI ArcGIS)

Contents

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Viewing Lowell City GIS in a web browser

There are many ways to view maps and spatial information on the Internet. The simplest is a web browser. To view the Lowell City GIS mapserver in a web browser, just open the URL http://gis.lowellma.gov. GIS features are limited but access to an interactive map could not be simpler. Layers are selectable; identification of features is possible, as is zoom, pan and selection, and a measuring tool provides point to point distance measurements.

gis.lowellma.gov-s.jpg

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Viewing Lowell City GIS with AEJEE

ESRI, the dominant vendor of professional GIS software tools, has established its product ArcIMS as a proprietary system for creating web mapservers. Many public mapservers, including those of the City of Lowell and MassGIS, use ArcIMS. One advantage of ArcIMS mapservers, is that their data can be viewed and manipulated much more freely in a GIS viewer program than in a web browser, making it possible to perform significant analysis tasks, and produce professional quality maps, using mapserver data.

ESRI has offered many free GIS viewers over the years. "ArcExplorer for Education, Java Edition (AEJEE)" is the first to offer nearly complete GIS workstation capabilities in a free downloadable program -- and especially, the first to offer access to ArcIMS mapservers in a free GIS tool. To use AEJEE to view Lowell GIS:

  1. Download and install AEJEE from http://www.esri.com/aejee. (A MacOS version is available as well as Windows)
  2. Start AEJEE
  3. Click on the large yellow diamond with a plus sign, to add a layer. Scroll down to the bottom to choose "Internet Servers"
    1. aejee-content-chooser-s.jpg
  4. Double click on "Add Internet Server" to open "ArcIMS 4 Connection", and enter the URL http://gis.lowellma.gov; click OK to see the available map compositions.
  5. There are several maps available; choose "public_SDE_AMS" for the same data that is available in the web browser; click OK.
  6. This map contains one map service of the same name. Select it and click OK.
  7. The same data available in the web browser mapserver is now available in this GIS viewer.
    1. gis.lowellma.gov-aejee-s.jpg

The toolbar and content pane on the left are simplified versions of those in ArcGIS. To investigate the tools provided by AEJEE to examine this data, read the tutorial provided on its download page.

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Viewing Lowell City GIS with ArcGIS

The main restrictions on manipulating the map viewed with AEJEE are on the symbology (symbols and colors) provided by the mapserver, and on adding and editing layers. To perform analysis and make professional quality maps from mapserver data, it's necessary to use ArcGIS workstation GIS software, available in the UML-EEAS GIS Lab and elsewhere on campus.

  1. You will need to install ArcGIS on your Windows PC, or use the machines in the UML-EEAS GIS Lab.
  2. Select the Lowell mapserver either from ArcGIS or ArcCatalog
    1. In the left hand "Catalog" window of ArcCatalog click on "GIS Servers"
      1. Double click on "Add ArcIMS Server"
      2. Enter the URL http://gis.lowellma.gov
    2. In ArcGIS, open the "Content Chooser" window, and add an ArcIMS server, just as you did with AEJEE.
  3. There are several maps available; choose "public_SDE_AMS" for the same data that is available in the web browser; click OK.
  4. This map contains one map service of the same name. Select it and click OK.
  5. The same data available in the web browser mapserver is now available in ArcGIS.
    1. gis.lowellma.gov-agis-s.jpg
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Viewing MassGIS in a web browser

To investigate resources available from MassGIS, Massachusetts' state office for spatial data, visit http://mass.gov/mgis. Follow the link labeled "Make a map online" to http://mass.gov/mgis/mapping.htm, Under "Two ways to explore MassGIS data online" choose the link labeled "Browser-based Mapping Applications". The "Quick Links" section provides easy access to a variety of layered map compositions in interactive browser based mapservers. We will be working with the "Environmental Justice (EJ)" mapserver, which displays neighborhoods across the state with high minority, non-English speaking and low-income populations (based on 2000 U.S. Census data). (These communities are often located on or near current or historical brownfields and other sources of environmental contamination.) Such areas are the focus of EOEA's EJ Policy, which was developed to use state resources to ensure that EJ populations receive a strong voice in environmental decision-making. These older industrial communities are scattered all over the state, as can be seen in the web browser viewer (at http://maps.massgis.state.ma.us/EJ/viewer.htm):
ejv1.png

Lowell is one of these communities:
ejv2.png

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Viewing MassGIS with AEJEE

We would like to present a more professional map showing the EJ community areas of Lowell; we can do this with AEJEE. As we did before, connect to the ArcIMS 4 mapserver at http://maps.massgis.state.ma.us, and choose the "ej" map:

ejae1.png

By selecting the area for our map, and choosing the "layout view" we can create a more professional map:
ejae2.png

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Viewing MassGIS with ArcGIS

We would like to show these EJ communities over the City of Lowell formatted public map for reference, to show the proportion of the city that's affected by EJ issues. AEJEE provides some tools for selection of features from mapserver data (see the AEJEE tutorial for an introduction) but a much better solution can be had using ArcGIS. First open ArcCatalog, add the MassGIS server, and open the EJ map layers in ArcMap:

ej0.png

The Lowell area EJ map in ArcGIS provides much more information:

ejl1.png

ArcGIS allows us to select and extract only the EJ areas (polygons) from this map. (Details are beyond the scope of this demo.)

ejl2.png

This Lowell EJ layer can then be combined with the City of Lowell mapserver data:

ejl3.png

These operations are not difficult, but do require some experience with ArcGIS.

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