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The Streets of Lemon Grove INTRODUCTION Ali Yost, Marlem Rivera, Pej Zaimaran and Teresa Ramos San Diego State University CLEANING OUR DATA WITH LINE SMOOTHING LINE SEGMENTS MAP CHALLENGES CONCLUSION The City of Lemon Grove does not currently have an accurate database of street measurements or precise locations and has thus far relied on Google Earth as a reference for city planning purposes. In partnership with the Sage Project, we will be addressing the question: Where are the streets in the City of Lemon Grove located and what are their measurements in length and width? By answering this question, the City of Lemon Grove will have a rudimentary framework for addressing future areas of concern such as emergency vehicle access, sewage lines, street signs, and sidewalk accessibility. Though our study area will only focus on a section of the city, other SDSU students collaborated in the efforts to data base street segments with the goal of data basing as much of the city as possible. The completion of this new database of street segments could be used to enhance and update the City of Lemon Grove’s General Plan through various facets as determined by the city. We walked the street of Lemon Grove with our smart phones in- hand to measure street lengths and widths through Collector for ArcGIS by ESRI. We tried the two different measurement methods offered in Collector: streaming and dropping points. We measured the street lengths by using the “Streaming” option in Collector for half of our study area and the dropping points option for the other half. The streaming method dropped points of our location for us every 5 seconds and produced a line with multiple points on it. We used the drop points method by dropping a point on one side of the street and walking across it to the other side. In attempt to be efficient with our time while still collecting accurate data, we measured the width of each street segment only twice (at each end of the street segments) and made the assumption that the street widths were the same throughout the middle of the street. Many challenges arose in our attempt to collect accurate data. Since the smartphone mobile application, Collector, relies on satellite signals to receive and transmit information, errors in line segment location occurred while we were walking to drop points, stream, and measure. We noticed obscure line segments and measurements that appeared on the map. These were likely caused by different obstructions to the signals such as taller buildings, large trees, or cloud cover. Additional factors that may have contributed to the errors that arose in our data collection using the stream technique could be lack of sidewalks causing us to walk into the street to avoid parked cars, user error of not being mindful to walk in as straight of a line as possible, and glitches on the Collector application that misread our location and dropped incorrect points. These challenges were overcome by either re-walking the line segment or editing the line later through line smoothing. Though we corrected the discontinuity created by using the stream method, we cannot correct for the errors due to glitches or cloud cover as they are simply out of our control. We found that the best way to collect data for street lengths and widths was to drop one point to begin the line segment and another to end the line segment. Though the streaming method was just as accurate as the dropping two points method, it caused more work for us in the end as we had to line smooth and readjust the locations for most of the lines created by streaming. However, the streaming method was extremely useful for streets that were curved, such as cul-de-sacs, as it gave a very accurate and aesthetically pleasing representation of non-linear road lengths and widths. To summarize, we would recommend only to use streaming method for curved or uniquely shaped streets. With help from The Sage Project, we were able to answer the questions regarding the location and length and width measurements of streets, by physically collecting and editing data for the City of Lemon Grove on Collector. We helped create a data base containing accurate streets locations and measurements of the length and width of the streets. We hope that this complete data base enables the City of Lemon Grove to make any needed upgrades to its city and master plan. ACKNOWLEDGEMENTS We would like to thank our professor, Crystal English, and the SDSU Geography Department for bringing this opportunity to our attention and for providing direction as we gained familiarity with a new data collection platform. We would also like to thank The Sage Project and the City of Lemon Grove for designing and supporting a program that allows students such as ourselves implement lessons learned in class in a real world setting. METHODS Final map of our study area with line segment measurements shown in red We used the “Line Smoothing” technique to correct for errors that arose during our initial data processing due to the fact that we used the “Streaming” technique to measure street widths. The “Streaming” technique drops points of your location every few seconds and provides a more accurate location of your route, however, since there are no sidewalks on many streets on Lemon Grove, our path varied as we walked around cars parked along the side of the street. For the purpose of measuring street lengths, “streaming” was not as useful as dropping two points per street segment because we wanted a straight line from one corner of the street to the next. Line smoothing on the Collector app allowed us to present our line segment data in a more visually appealing way while keeping our data accurate. See the difference in presentation of our data before and after line smoothing below. Click this button once to start a line segment and again to end it to create straight lines with only two points Click once to delete points on line segments to fix inaccurate points created by glitches, or to smooth lines Click this button to begin streaming and points will be dropped at your location at set intervals Section of Lemon Grove map with line segments measurements shown in red
