What You Can Do With the Javamap Web Applet

Quick Links ACS Profile Reports ACS Trends Reports SF3 Profiles (2000) Circular Area Profiles SF3 Trend Reports Detailed SF3 Profiles IRS Migration Profile Missouri County Data Map Applinks Master Menu MABLE/Geocorr 2K RxA Cure for the Common Codes American FactFinder Overview When you access a map on the MCDC web site that has been generated with the javamap tools you are not getting the traditional map-as-a-graphics-file. Rather, what you have is a mini-application (java applet) that displays a default starter map and then allows the user to modify that map to suit their needs and preferences. The purpose of this document is to provide a quick summary of what we think are the most important things the applet lets you do and how you do it. For an alternate description of the applet (by its authors) you can access the Map Applet help option on the popup menu that is displayed when you right click on the map. Our purpose here is to provide some additional guidance on what can (and perhaps should) be done and how. General Things to Know You must have the java 1.4 plugins installed for use with your browser. If you do not have them installed and you are using Internet Explorer you should be prompted to go ahead and downloand and install the plugin. Not everybody can do this, however, depending on their environment. For example, if you work in Missouri state government you will not be allowed to do such a download-and-install yourself. You may need to have authorized personnel at your site do this installation for you. The applet has been successfully tested in WindowsXP environments with the popular browsers: Internet Exlorer 6.x, Netscape 7, Mozilla 1.7 and Firefox 1.x . We have tried and been unable to get it to work on Macs using IE5.5 and Safari. When you initially load a map generated with javamap there is a considerable amount of data and software that must be accessed and loaded into your PC's memory (RAM). This can take a while (ten or twenty seconds perhaps), for large, complex maps. If your machine is strapped for memory (say, 128 meg or less) there is the possibility that there will not be sufficient memory to load what needs to be loaded. Once this initial loading is completed, however, the applet is able to handle requests for changes and to redisplay the map rather quickly. Because you are working with a dynamic application rather than a static image there is no way to capture the map image as you normally would with your browser (by right-clicking on the image). If you need to save the map image you will need to use a special screen capture software, such as SnagIt. Details of how this might work are beyond the scope of this document. The learning curve for using the basic features of this applet is about 15 minutes for most users. To master all the various options including the many style features (most of which need not ever be learned), could easily require several days. Because it is a java applet, it will be "cool", but it can also be finicky and a little unpredictable. You need to be patient to let the application complete what it's doing, or run the risk of doing something to confuse the applet. (It's not always clear that the applet "got" your last click and that it's working on it.) In most cases, when things get messed up they can be fixed by doing a a page refresh. (But not always). What and How Here we provide an array of things you can control about the map, directions on how to do it, and comments regarding any limitations or suggested settings. What How Comments Change the "map variable". Properties - General - Region color pulldown Nearly all the maps we generate will be choropleth, with each region assigned a color based on the value of what we are calling the "map variable". When you change the map variable, you need to then go to the Categories tab and make a change in order to get your new map. That "change" does not have to significant; you can just change the Intervals count by making it go up 1 and then down 1 (a net no-change). But the applet needs to process a categories change in order to update the value intervals used. Change the way the "map variable" controls colors. Properties - Categories. By default you get intervals determined by "Equal counts" for a specified number of intervals. This will often be quartiles or quintiles. You can modify the number of intervals, or you can substitute "equal width" for "equal counts". Equal widths are generated by taking the maximum value minus the minimum and dividing that interval into the specified number of equal width sub-intervals. You can also choose "Continuous" or "Unique" but these are rarely used. Specify whether to use a color ramp. Properties - Categories - Use color ramp check box. To actually change the color used in the color ramp requires using Style Editor (not Properties) and then choosing from Color scheme dropdown. They use non-mnemonic names for these, nothing as simple as an actual base color name. You'll have to experiment to find one you like. If you choose not to use a color ramp the default colors are good in that it is easy to distinguish the categories, but they are rather randomly assigned so it is not easy to detect which values are higher or lower. Turn on/off region labels (annotation) Properties - General - Advanced options - Show annotation checkbox. Most maps will have annotations provided and turned on (e.g. a Mo county map will have the county names displayed on the map). Why turning these on and off is considered an "Advanced" option we don't know. Not to be confused with the following "chart IDs" option. Turn on/off display of region ID and initial variable value. Properties - General - Show tips with variables checkbox and Chart tips variable select list. This is a very handy feature which will always be turned on by default. It instructs the applet to display the region ID value and the response value (of the initial map) when the cursor is placed over a region. Unfortunately, you can only select these 2 variables and even when you modify the variable that controls the region color or height, this does not result in the new variable becoming the one that is displayed using this feature. If you only want to see one of these variables then you can deselect the one you don't want from the select list in the Chart tips section of the Properties - General tab. Turn on/off region markers. Properties - Markers - Show markers checkbox. Once you turn on markers you can also control their properties from the Markers tab window. Usually, when you choose them, you will want to turn off annotation (because the region labels and the markers will be displayed in the same place, causing map clutter and unreadable labels), and you will also want to use Properties - General - Marker (color/height) to specify which variable(s) will control the color and/or height of the marker. A good way to use this feature is to have a quality measure variable to control the regional shading and then a corresponding quantity variable that controls the height of the marker. E.g. if the map colors depict "Percent Poor", the using "Poor Persons" to control the height of the markers makes for a very useful map. See next entry for a display tip. Change the viewing angle to better view 3-dimensional maps. Map Toolbar - rotation tool - drag on map. The Map Toolbar feature almost makes you think you are using a true desktop GIS. The rotation tool is the 2nd from the left. Click on it, then move your mouse back to the map and drag it around. When you have associated a variable with marker heights you will see that as you rotate the viewing position these "data towers" become much more visible and easy to interpret. Zoom in and out to see more or less map detail. Map Toolbar - Zoom tool - drag mouse up on map to zoom in, down on map to zoom out. In conjunction with the pan tool you can eventually navigate your way to the specific part of the map you want to view more closely. Put your mouse near the bottom of the map and move up (north) to cause the map to zoom in and reverse (drag from north to south) to zoom out. The area in which the map is displayed does not change so when you zoom in parts of the map are no longer visible. Not exactly state of the art, but better than nothing. Drill down to another map or related web page. Left click within a region of the map. What happens when you click within a region depends on how the map was generated and so will vary. We will try to use a subtitle at the top of the map to inform the user of what the "drill-down" capabilities of the map are. An example of how this might work is when viewing a state wide map of Missouri counties, you might be able to click on the map and it would take you to a map that just displays the counties for a region. (And perhaps on that region-level map if you clicked within a county it would take you to a map of that county by census tract.) Sometimes, we'll generate maps with no drill down specified, in which case left-clicking will simply select the region. But there are special capabilities of the applet that are affected by such selecting other than the region's outline is highlighted. Control the map legend. View - Region legend Region legend on the View page is just a toggle to control whether or not the legend will be displayed, which it will almost always be by default. Use the Style Editor (right click) to control things such as text and line styles associated with the legend. Get help regarding a specific menu or menu choice arrived at after you right-click. Right click - Help - Map Applet help. This document is more of a tutorial but the online help is the ultimate reference and is organized to follow the menus. Capture the current map image to a gif file. No such capability within javamap, per se. We talked about this above. There is no general solution to this. However, there are software tools that will let you capture anything that is displayed on your screen and these can be used. At OSEDA we use a product called Snagit that handles this task quite well. Hyperlinks at Bottom of the Page Most of the maps we generate will have a row of hyperlinks near the bottom of the page. One of these is a link to this page and it is likely that is how you got here. Another (usually, but not always present) takes you to the MCDC's web utility data extaction program, dexter, with the dataset used as the source of data for the map pre-specified. If you are not already familiar with dexter (and its navigation tool companion uexplore) you will probably want to simply ignore this link. But if you know about these tools (or want to take the time to learn about them -- see the links at the bottom of the page to the online dexter tutorial) then this is the way to get access to the raw data that was used in creating this map application. You may need to specify a filter and/or a list of relevant variables to keep, i.e. the data set we used may have more geographic areas summarized (rows/observations) and more data items (columns/variables) than were needed for the map. Note that each of the hyperlinks here will result in opening a new browser window. Credits and Technical Stuff The javamap applet was written by SAS Institute and is part of the SAS/Graph software package. We (at the Missouri Census Data Center / OSEDA) have not in any way modified that applet. It would not be technically nor legally feasible for us to do so. Instead, what we have done is focus on using the tools provided within the SAS (c) software package in order to create a number of map image files with convenient access to a wide array of data (from the MCDC public data archived) and with what we hope will be useful drill-down capabilties for our users. The normal way SAS users are expected to generate the html pages that serve as the means of invoking the applet and passing it the complex myriad of parameter specifications that it needs to build the map application is through a procedure in SAS/Graph called Proc GMAP. A serious limitation of using that tool to generate the javamap files, is that it can only generate a single mapping variable. The applet is capable of handling any number of such variables, but GMAP does not generate the appropriate XML specifications to do so (it only recognizes a single "map variable"). The Missouri Census Data Center would like to thank Dr. Hendrik Meij of Wesleyan University for his essential contributions to the building of the MCDC's tool (a SAS macro) that is capable of generating the same kind of javamap html files that proc GMAP will, except that the ones it generates can have multiple response variables. Not only did Dr. Meij share with us his discovery of the additional capabilities of the applet beyond what was indicated in the SAS technical documentation, but he also contributed many hours of technical assistance in helping us to build and debug the macro that we now use to generate the map files. The javamap macro and this web page were both written by John Blodgett of OSEDA, under a contract with the Missouri Census Data Center.

This file last modified Wednesday April 27, 2005, 09:12:14