In the process of developing the Pilot Program for the Water Facilities GIS, the Thomas Bros. street centerline database was used as a backdrop for "head-up" digitizing to build the water main network system using a custom conversion program. The water main network also served as a base map for the WFGIS.Valves, Fire Hydrants, Leak Locations, Reservoirs, Tanks, Pump Stations, etc. were also digitized and built into separated coverages. Datasets from many different formats were then integrated into GIS environment, Arcad and ArcView, and linked to the coverages. Using ArcView 2 with its programming language Avenue, a friendly and easy-to-use application was built and delivered to the end users with accurate and updated geographic water facility information at their finger tips . With WFGIS, it is expected that the end users will dramatically reduce the time spent looking for data necessary for their daily work, as well as provide faster response to emergency situations.
This paper will focus on the questions, problems, and obstacles that were encountered and examples of activities will be discussed.
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Currently, the Graphics, Maps and Records Group (GM&RG) of the Department manually maintains two major map sets. One set is known as the Water Service Maps, which are maps at a scale of 1 inch=100 feet, and are based on the North American Datum 1927 (NAD 27) California State Plane Coordinate System. The Water Service Map set depicts all Water System property and facilities such as reservoirs, tanks, wells, pumping and regulator stations, mains, fire hydrants, gate valves, water services, etc., as well as the geography of the areas served. Each map covers an area of approximately 1/4 square mile and represents a detailed layout of the water distribution system.
The other map set also manually maintained by the GM&RG is the Gate Section Maps, utilizing a scale of 1 inch=600 feet. Each Gate Section Map covers an area of approximately one square mile, and shows information pertaining to the location and description of gate valves. The maps of the entire city of Los Angeles water system and the supportive tabular data are kept in five books--one book for each of the five districts. Each of the five water operating districts keeps from 50 to 75 copies of each Gate Section Map book for their district for use by supervisory and field personnel. The maps are widely used by field operations and maintenance personnel for normal and emergency situations, including water main breaks. This map set was chosen to be the base map for the WFGIS applications.
Similarities were noted between the manually drawn Gate Section Maps and the newly developed Thomas Brothers street guide digital street center line database. The Thomas Brothers street layout maps, which are extensively used in California, closely matched the manually drawn Gate Section Maps. This meant by using the Thomas Brothers digital maps as background graphics, the conversion of the Gate Section Map could be done quickly by tracing over the Thomas Brothers digital maps using AutoCAD.
For the conversion of our maps, the free flow of data between GIS and CAD allowed by ArcCad proved to be invaluable. The scale of the original Gate Section Map is 1"=600�. If the valves, hydrants and other equipment were drawn on the Gate Section Map in their exact location, the map would be unreadable, especially in intersections and congested areas. As a result, the maps have to be exaggerated. Two valves, for instance, that are actually only two feet apart must be plotted more than 30 feet from each other. The fire hydrant symbol alone is about 50 feet wide on the Gate Section Map. This is actually a convenience for us during conversion. Since accuracy is not a critical factor, the Thomas Bros. street centerlines (converted into an AutoCad file through ArcCad) can be used as a template and simply traced over. This method is a lot easier than digitizing a Gate Section Map and will actually produce a map that is more accurate than our current one.
The main function of our application is to collect and manage the data necessary to translate the AutoCad maps into a GIS system through ArcCad utilizing extended entity data.
ArcCad translates polylines into single entities provided there are no arcs within the polyline. In the case of an arc within a polyline ArcCad breaks the polyline at the arc into two separate entities. To maintain a continuity between pipes in a Gate Section Map, all pipes must be represented by continuous polylines, broken only at pipe changes and intersections. All curves in the pipe must be represented by several vertices arranged along the curve. The WFGIS application allows users to enter curves in the familiar way that AutoCad allows, but it draws vertices instead of AutoCad Curves.
AutoCad symbols, or blocks, can appear in any form that they are created and can be scaled or rotated depending on the desires of the user. ArcCad translates AutoCad blocks as points, the point of a block being the coordinates of the block insertion point. Once translated, any AutoCad block looses all distinguishing features save that of a point. Also, currently in ArcCad and ArcInfo a point symbol cannot be scaled or rotated. This is the reason for creating the fire hydrants as polylines rather than points. Each hydrant must be a single continuous polyline shaped and doubling back on itself where necessary to form a hydrant symbol.
Computer maps do not need details because of their ability to zoom in to congested areas. Until we can get everyone in the department who uses the Gate Section Map a computer, we need to produce a hard copy at least as good as the manual version. The detail areas must remain continuous with rest of map but also at a reduced scale so that they may be enlarged. One solution to our detail areas would be to place the facilities in the drawings for the GIS to read, and then create another AutoCad drawing for the details. To solve the problem more efficiently, we built in the ability to globally reduce the scale of all equipment for working in the detail areas. For plotting we can now open a separate AutoCad viewport for each detail and zoom in. This eliminates the need for creating a separate drawing and the details automatically update to any changes in the map.
The Gate Valves, Fire Hydrants, and Pipes will all be converted into GIS coverages. In the case of the valves and hydrants, existing tabular databases will be joined with the graphics to create larger GIS datasets. No database currently exists on the pipes other than what is recorded on the manual maps, so a new database will be created.
When joining an existing database to the GIS dataset created by ArcCad, unique identification records for each graphic entity must be created. Functions related to identification numbers and interconnectivity between the symbols on the map are handled transparently and do not affect the user in any way. Along with managing new identification numbers, WFGIS automates as much of the data and graphic entry as possible in order to simplify the computerization process, address the graphic requirements needed for the GIS translation, and maintain a high level of quality.
A complete set of coverages is created for each Gate Section Map file so that any larger segment of the city can be created by simply appending the appropriate Gate Section Map coverages. This concept addresses the large amount of memory required to load several AutoCad Gate Section Map files at once before building topology, as well as the time involved in rebuilding a large coverage for minor map revisions.
The Graphics, Maps and Records Group maintains the Master Database of the Gate Valve Inventory, the Master Database of the Table Codes and a mirror of the Fire Hydrant Inventory. The Master Database of this Fire Hydrant Inventory is on the Mainframe. The GM&RG personnel updates the Gate Valve and Fire Hydrant databases daily and copies of these databases are sent to the District Offices periodically.
Copies of these databases are also converted into "dbf" format to be linked to the WFGIS applications running on ArcView, a GIS product of Esri (Environmental Systems Research Institute)
The AutoCad files are then built into coverages to be used with ArcView. They are built in district level (every coverage includes the entire district).
(213) 367-1124 Kien Hoang
(213) 367-1123 Greg Ammon