Rio Grande Basin Initiative

Webb County Mapping Service

If this is your first time using our services, please take a few moments to read the entire page before proceeding to the mapping site.

Select one of the links below to begin the mapping application.
Maps open in a new window.
For slow internet connections
or low screen resolutions

Dial-up users, 800x600 view
For fast internet connections
or high screen resolutions

Broadband users, 1024x768+ view
What is ArcIMS technology?

This site uses ArcIMS technology. ArcIMS is a powerful GIS application that will allow you to manipulate GIS data in several ways. You can:

  • View information about various data layers, such as Watershed Boundaries, Major and Minor Aquifers, and Roads.
  • Find a City, Stream, Soil Type, Road, and more.
  • Build your own geographic queries to pinpoint a location.
  • Locate an address, measure distances, and create buffers around specific features.
  • Create your own custom map, complete with title and legend, and print it out.
What are layers and layer groups?

A layer is a set of data that can be made visible on the map. For example, the Cities layer contains data for each city in the county. By making this layer visible, you will be able to see the cities on the map.

The various data layers are organized into folders.

After clicking on the Layers button, you can expand the folder groups to see the layers associated with a particular group.

How do I make layers visible on the map?

To the left of each layer's name on the Layers page is a check box that governs whether or not a layer is visible.

Check the box to see the layer on the map. If you are unable to do so because the box is grayed out, this means the layer cannot be seen at the current extent of the map and therefore cannot be made visible at this time.

To zoom to the extent on the map where the layer can be seen, simply click the magnifying glass next to the layer's name. You will now notice the check box next to the layer's name is no longer disabled, and you may check the box to make the layer visible on the map.

What is the active layer?

In order to use any of the mapping tools, you must first select a layer to analyze. This layer is called the active layer.

To make a layer active, you first must make it visible on the map by checking the box next to the layer's name. Upon doing this, you will notice the layer's name is now a clickable link. You may now make the layer active by clicking the layer's name.

The active layer's name is highlighted in yellow, as well as shown in the frame directly below the map itself.

I made a layer visible, why can I not see it on the map?

Layers are drawn on the map from bottom to top, denoted by the order in which they are listed.

This means, the last layer listed* on the Layers page is the bottom most layer. It is drawn underneath all other layers on the map. Therefore, if the layer listed above it is also visible, it may be obscuring the layer below it.

If you would like to see the layer below, simply un-check the box next to the upper layer's name.

*This means the last layer listed in a folder group. The folder groups are not in order, so layer 4 from one group may be drawn underneath layer 4 from the group below it.

How do I view the map legend?

To view the map legend, simply click the Legend button which is located directly next to the Layers button.

The legend is only for those layers currently visible on the map.

Where can I go to learn how to use the available mapping tools such as Zoom In, Identify and Find?

To learn more about our Interactive Mapping Service, and to learn about the mapping tools, please refer to our online help file.

To view the help file, simply click the link at the bottom of this page.

If you would like to take a step by step tutorial on how to use the mapping application, refer to the tutorial file, listed above the help file at the bottom of this page. Please note, the tutorial is in Portable Document Format.

How do I start the mapping application?

To start the mapping application, click one of the links at the top of this page.

You have two choices: a low resolution map and a high resolution map.

If your monitor is set to display 800x600 pixels or if you have a dial-up internet connection, select the low resolution map (left link).

If your monitor is set to display 1024x768 pixels or higher and if you have a fast, broadband internet connection, select the high resolution map (right link).

Quick tutorial
Online help system

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