Home Map Help FAQ Trouble

Frequently Asked Questions and Answers

Q. What if I believe incorrect gun offender information is shown on this web site?
A. Although every effort is made to keep this list accurate and current, the city cannot guarantee the accuracy of this information. Offenders may have moved and failed to notify the Chicago Police Department as required by ordinance. If any information presented in this web site is known to be inaccurate please contact the Chicago Police Department at Criminal Registration Unit, 3510 S Michigan Ave, Chicago, IL 60653.

Q. Why can't I see the specific addresses of gun offenders?
A. Addresses shown at the block level only, and specific locations are not identified. This is done to protect the privacy of the individuals. Although general locations can be seen on a map, these placements cannot be used to derive the specific house or location where the offender resides.

Q. Why is the search distance limited to 1/2 mile?
A. A half mile is 4 city blocks which should be sufficient for examining gun offender information around an address, school, or park. This was also done to reduce the load placed on the web server.

Q. Why do I need to turn off my web browser pop-up blocker?
A. This site uses pop-up windows for several reasons. The primary reason is to maximize the size of the map image by removing unnecessary toolbars, address bars and button bars from the browser window. The Back button on a web browser does not function properly with CLEARMAP and removing it eliminates a potential source of error. Additionally because the application uses framesets it makes printing difficult so, the Print feature opens a map image in a pop-up window. The MapLink feature and the Table printing feature also take advantage of opening new browser windows.

Note: Most modern pop-blockers whether native to the web browser or part of an add-on toolbar like Google or Yahoo allow you to add this website (http://gis.chicagopolice.org) to a list of websites that are allowed to use pop-ups. We recommend taking advantage of this capability to keep your pop-up blocker on while enabling CLEARMAP to function properly.

Q. Why do I need to zoom in close to view gun offenders?
A. The gun offender points aren't shown on the map until only a few city blocks are shown in the window unless the user searches for offenders around a specific address, school, park, ward or community area. This is done to improve performance and make the map easier to read. Showing all offenders at a citywide scale would be useless for the viewer. The map would be nothing but a blob of overlapping points.

Q. Can I just pan around the Map viewing gun offenders?
A. Yes, you just need to be zoomed in close enough and if you've used a Search By function like Address click the MapView button to remove any geographic restriction. See the question below.

Q. What does the MapView button do? Why is it important?
A. The MapView button located beneath the map on the right side of the Search By: section is used to remove any geographic restriction you may have placed on the map. For example, when you Search By: Address a red circle is drawn around the address and only those offenders that fall within the circle are shown. If you click the MapView button the circle is removed and you will see any registered offenders that reside outside the circle that are within the map window. You can then freely pan around the map viewing offenders. If you zoom too far out on the map without a geographic restriction the points will disappear. Just zoom in closer and they will reappear.

The MapView button removes all the other geographic restrictions like beat, district, ward, community area, school, park, and polygons drawn using the Draw Shape tool. If you see an area bound by a red line clicking MapView will remove the line and the geographic restriction.

Q. How does the Draw Shape tool work?
A. The Draw Shape tool (left side- middle) allows you to draw your own geographic boundaries instead of using an address, beat, ward, etc. Click Draw Shape to activate the tool. The tool has 3 methods.

1) Double-click once on the map creating a Point and a circle with a radius of 660 ft. (1 city block) will be drawn and points inside of it shown.

2) Make a Line Selection by single clicking once, moving the mouse and double-clicking to complete the line.  Points on either side of the line will appear inside a box.

3) Create a Polygon by single clicking several times and finishing with a double-click. Do NOT try and close the polygon the last double-click will close the polygon. For example, to create a triangle (3 sides) click once, move mouse, click once, move mouse, double-click. The triangle will be completed and the points inside shown. Important: when using this tool do not draw lines that overlap, if you do the tool won’t work.  You are limited to a polygon with 10 vertices

If you make a mistake, click the Draw Shape button and start over.

Q. How does the MapLink feature work?
A. The MapLink feature enables people to share a common map view using an encoded URL link. This can be useful for facilitating a discussion about registered gun offenders in a particular area. When you press the MapLink button a new web page is open with the URL link and a list of the query parameters. The query parameters include the location, visible offender types and any filter parameters.  The best way to share this information is to copy the entire page into an email. A quick way to do that on a Windows PC’s is to use Ctrl A (Select All), Ctrl C (Copy), open the email page and press Ctrl V (Paste). Copying the entire page lets your email receiver know where this information came from (gis.chicagopolice.org) and what parameters you had selected when you created the link. Give it a try and remember the receiver needs to be using a supported web browser.