The Institute for Mapping Technologies

Archive for the ‘data sources’ Category

Creating a shapefile Layer in Quantum GIS

Monday, April 8th, 2013

In Quantum you can create either a point, line or polygon layer.

Layer>New>Shapefile Layer

Shapefile Layer

Then you can either choose to create a point, line or polygon layer. Before choosing think about the data you are using and what you are creating. If you are working with US Highways and are now creating a layer that just includes highways in Texas you want to choose line for the type of file you create.

For this example Line was chosen as the type of layer.


Next choose a CRS or coordinate Reference System. You can either leave it as the default and then change it later (see below) or you can set it when you create the layer.

You’ll notice that the id field is automatically populated. You can delete this field if you don’t want it there. Select id and then click remove attribute.


To add an attribute:

Under ‘New Attribute” type in the name select the Type  of data the field can hold. You have several options. One is text data this refers to letters or numbers. Then you can choose whole numbers. This refers to numbers such as 100, 300, 500, 10,15,1000. You can not input decimals into this field. Lastly there is decimal number. This includes numbers such as 12.15, 11235,2569843.

You can also choose the width and the precision. Width can be set with all fields. Whole, Text and Decimal. Width refers to the number of characters allowed in the field. This includes punctuation and spaces.  For whole numbers the maximum width is 10. Precision can be set when decimal is highlighted. Precision is the number of places allowed after the decimal. It is entered as zeros in the precision field.


Once everything is set click on add attribute.

And it will appear in your list below. You can continue like this and add as many field as you like. They can be a mix of text, whole or decimal.


Once you are done click ok. It is going to ask you to choose a location to save. When you choose a name to save it as it will give it that same name in the attributes table but you can always change that later.


If the CRS was not set when the layer was created. You can set it now. Right click the layer and then go to set layer CRS.


Then you can set the CRS.


Lastly save the layer.

Right click>save as




You have several options.

Choose the format . It defaults to ESRI shapefile.

Give it a name and choose where you want to save it.

Then you can set the CRS here also.

Layer will leave the CRS as the default. Either WGS if you made no changes when you created it. Or what it was set to when it prompted for the CRS originally. Project will set the CRS to what the project is, if that was set up. Lastly is selected where you can browse and set the CRS to what you want.






Once your done click ok!


Videos out on How to get Free Aerial Imagery!

Monday, December 5th, 2011

The USGS has a wealth of imagery, both current and historic. We’ve just created several videos that help explain how to find and download free aerial imagery from USGS. These are great guides for all to learn the complicated USGS interface.

The USGS has several platforms to deliver data, the main 3 are:


  • EarthExplorer
  • Seamless


Each has quirks and none are very user friendly. We think they are powerful and want to help you learn to use them to get great aerial imagery.



How to find low res large scale imagery off of GLOVIS



How to find Historic Aerial Images off of USGS EarthExplorer 1 of 2



How to find Historic Aerial Images off of USGS EarthExplorer 2 of 2



How to download High resolution orthoimagery off of EarthExplorer





More Texas GIS data sources added

Tuesday, October 5th, 2010

We are fortunate in Texas to have a plethora of  GIS data sources for the state. Today we found a few more links to sources and have updated our FREE Texas GIS web page to reflect these news.