DNRGPS and Michigan GeoRef coordinates

DNRGPS, the new replacement for DNRGarmin, does not handle the Michigan Georef projection properly. If you load an existing shapefile in Michigan Georef coordinates into DNRGPS, the latitude and longitude values are changed to the wrong part of the Earth (About 25 degrees of latitude is added and longitude is changed from ~ -88 to 175 degrees: a change of almost 265 degrees). Similarly, if data is transferred from your GPS to DNRGPS and the Michigan GeoRef projection is then applied, the latitude and longitude values stay correct, but the projected coordinates (used by ArcGIS or other GIS software) are changed so the data are on the wrong side of the Earth.

To avoid problems with your data ending up in the wrong hemisphere, do the following:

 

1) If transferring data from your GPS to GIS software, use either unprojected (“no projection” in DNRGPS, which = WGS84 lat/lon) coordinates or the appropriate UTM zone for your part of Michigan (zone 15N in the extreme western UP, zone 16N for most of the UP and the western 2/3 of the LP , or zone 17N in the extreme eastern UP and the eastern 1/3 of the LP). See figure 1 for UTM zones in Michigan.

 

Figure 1 - MI UTM zones
Figure 1 – UTM zones in Michigan (click for a larger version)

 

If you need your spatial data to be in Michigan GeoRef coordinates, use the Project tool in ArcGIS (or the reproject function in your GIS software if you are using another package) to convert your data to Michigan GeoRef coordinates.

 

2) If you are transferring data in GIS format (shapefile or geodatabase) to your GPS and it is in Michigan GeoRef coordinates, you should first reproject it to either Geographic coordinates or to the appropriate UTM zone.

I have filed a bug report with the developers of DNRGPS, but they have more than a hundred other issues to fix so it may be a while before this is resolved. Fortunately, this is a non-fatal error and can be avoided with some planning.

ArcGIS application errors – some troubleshooting tips

Twice today I’ve seen problems with ArcGIS 10 (and 10.1) failing to launch. In one instance, no specific application error was given – ArcMap just failed to start with a ‘serious error’ dialog, and in the other, some direction was provided by ArcMap in the form of an error message.

In both cases, the user had a corrupt default user geodatabase. The location of the default geodatabase may be given in the error message. If not, it should be located in <user profile>\My Documents\ArcGIS. If you are working on a lab machine, the location will be h:\ArcGIS\  The file is named Default.gdb, and if ArcMap has had trouble loading more than once, you may have multiple copies named Default.gdb, Default.gdb1, Default.gdb2…

The ESRI knowledge base article 38523 suggests several fixes, the most important of which seems to be deleting any Default.gdb files in the users profile directory. I found that using Windows worked properly, as ArcCatalog seems unable to remove the offending files. One machine I worked on today had more than 150 default.gdb files (all of which were corrupt and preventing ArcMap from launching).

Tutorial – formatting tabular data for joining to ArcGIS features

Here is a short tutorial that outlines the steps for formatting spreadsheet (tabular) data in preparation for joining it to features (points, lines, or polygons).

If you aren’t familiar with joins, they allow you to attach attribute data that is separate from (external to) your features. In order for joins to work, a common field that contains a unique identifier is needed in both the features and the external data. A join will match records in the external data table to features in the GIS layer based on the values in the unique ID field.

An example of features and data that have this relationship is Census tracts, which change infrequently (features). To the tracts you can join any number of metrics collected or calculated by the Census bureau: residents tabulated by race, income, education; housing stock and attributes (tabular data).

This is a very generic and basic tutorial. Please email with questions or comments.

Using MapTips in ArcGIS

It is often useful in a map to enable “MapTips” for layers in an ArcMap document. When map tips are on, hovering the cursor over a feature on the map will display the contents of a field from the attribute table in a pop-up window. This eliminates the user’s need to use the Identify tool on a layer.

To turn on map tips, open properties for the layer and choose the Display tab. In the Display Expression box, select the field you would like shown in the pop-up and check “Show map tips using the display expression“.

However, you may find this option unavailable (“grayed out”) when trying to enable map tips.

This is usually caused by the layer not having a spatial index available (see this post from ESRI for more information). The solution is to build a spatial index. This may be accomplished two ways:

1) in ArcCatalog, navigate to the layer, select it, and open Properties. Choose the Indexes tab and click Add under Spatial Index.  

2) use the Add Spatial Index tool. In Arc Toolbox expand Data Management Tools > Indexes  and open the Add Spatial Index tool. Select your layer as the Input Features in the tool and click OK.

An advantage to using the ArcToolbox tool is it may be used to rebuild an existing spatial index. ArcCatalog may only be used to create an index if one does not already exist.

After creating a spatial index, the Show MapTips option should be available for your layer.

Instructions for installing the Education Edition of ArcGIS (1 year license)

I have had some questions about how to install and authorize the 1-year ArcGIS license available for education use. I improved the directions, available as a PDF or continue to read below… If you are interested in the software, installer DVDs are available from the help desk in the Library.

ArcGIS 10 Education Edition – 1 Year Licensed Software

The Education Edition of ArcGIS version 10 requires an authorization number that must be activated before use. An authorization number will be printed on the inside of the DVD sleeve, along with instructions for activating it. Visit www.esri.com/EducationEdition to activate the authorization number before installing the software. An ESRI Global Account is required. (If you do not already have an ESRI Global Account, you can create one at this website.)

FAQs for the software are available at   http://www.esri.com/software/arcgis/eval-help/index.html

Please note that the some of the FAQs currently are designed for the general purpose evaluation license, and any reference to the length of the evaluation term should be disregarded. The term of the Education Edition is 365 days and the license level is Arclnfo.

•Insert the DVD and choose ArcGIS Desktop  Setup

•Wait for the installer to load (authenticate as administrator if necessary), accept the license agreement, choose a Complete install, and install to the default location.

•After the install completes, click Finish and choose ArcInfo (Single Use). Click Authorize Now and choose “I have installed my software and need to authorize it”, “Authorize with ESRI using the Internet”, enter contact information, and enter your authorization number. Choose “I do not want to authorize any extensions” (and don’t evaluate any extensions either – they are included with your license).

You should download and install the latest service packs periodically, available from http://www.esri.com/ Support> Downloads: Patches and Service Packs. As of  March 2012, ArcGIS 10 SP 4 is current.

If you have questions, please contact mdhyslop@mtu.edu