Return to Geog 210 page<\/a><\/p>\n\n\n\n In exercise 6, you used a point layer containing crimes in the city of Worcester in 2014. Now, you will learn how to create this layer of the locations of crimes using street addresses, a process called geocoding. <\/strong>Crime data were obtained from crimereports.com<\/em> (deadlink). In addition to the table of addresses, we\u2019ll use an \u201cAddress Locator\u201d (more on this later) provided by OpenStreetMap<\/a>.<\/p>\n\n\n\n The address locator requires a vector street layer containing house numbers for each street segment. Since houses are arranged as odd\/even numbers on different sides of the street, the vector layer must have house numbers on both, left and right sides of the street. Fortunately this information has been compiled by the US census bureau in the street TIGER files. See the image for a look at one section of streets between South Hadley and Chicopee.<\/p>\n\n\n\n The figure below shows columns of the TIGER file for Massachusetts (from MassGIS). Notice the street name column: there are multiple line segments for the same street. The rest of the columns indicate the range of house numbers found on the left and on the right for each segment:<\/p>\n\n\n\n Be aware that this business of geocoding street addresses will vary enormously from country to country depending on the quality of the data and the situation of the addresses on each street in each country.<\/p>\n\n\n\n Question 3. How many records are there?<\/em><\/p>\n\n\n\n Notice the column called \u201cWeb_Address\u201d. This is how crimereports.com <\/em>gave you the address. Obviously, it\u2019s a degraded address. I edited those addresses (removed the word \u201cBlock\u201d) and created a column called \u201cAddress\u201d. The result of this operation is that all the crimes that happened in one particular block will be geocoded to the first address of the block.<\/p>\n\n\n\n The procedure we are going to use takes a long time, so we are going to get only a subset of the crimes in Worcester. For our purposes, we\u2019ll only study the Drug related crimes.<\/p>\n\n\n\n Next, we\u2019ll use a QGIS plugin. This is an external program that provides extra functionality to QGIS.<\/p>\n\n\n\n Question 4. How many unmatched addresses in the Not Found output csv file did you get? _____________ (It should be a very low number, hopefully)<\/em> <\/p>\n\n\n\n
\n\n\n\nPart 2: Geocoding (with QGIS)<\/h2>\n\n\n\n
![\"address](\"https:\/\/commons.mtholyoke.edu\/emarcano\/wp-content\/uploads\/sites\/965\/2025\/02\/ex9-fig18.jpg\")
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