I completed the assignment and now understand how to georeference CAD data. However, I have a few questions related to exporting. First, when you export the selected data, should you use the coordinates of the data frame or the layer's source coordinates? I choose the former, as I added the buildings layer first so the CS was in State Plane feet. Second when adding the newly exported data to a new data frame, the layers did not contain a CS. Did I do something wrong? And can I just set the CS to the same as the buildings layer? Or should they be set to the CS of the original CAD data? How's that for confusing.
Off to Morehead City with Herb for the weekend. Hopefully the weather will be okay.
Thursday, August 28, 2008
Tuesday, August 26, 2008
August 25, 2008
More homework, unbelievable. After trouble with Media Player and Internet Explorer, I was able to view the presentation. Have I mentioned my CAD class in college that didn't go so well? At least GIS is a lot more simple to understand. Let's see what I learned from the video.
With ArcGIS 9.2 they have improved the software's ability to match symbology, fonts, and rendering. Additionally you can now create world files to define the transformation of your data. A tool that seems quite useful is the two-point transformation, which maintains the aspect ratio of the CAD dataset. One can also scale, rotate, and shift a CAD layer to match the extent of an ArcMap layer.
What I would consider the greatest advancement is the capability of the software to translate CAD data into a geodatabase. This allows the user to edit a layer and apply more advanced cartographic representations. Similarly, one is able to convert a modified dataset back to CAD format. I can imagine this is quite useful as well.
Let's see, news from home. Not much exciting. We had a very relaxing weekend, including some hiking at Holmes Experimental State Forest. No quite as scenic as Dupont State Forest, but very solitary and nice. We also learned our apple tree produces Gala apples, so we will be making some apple sauce this week.
With ArcGIS 9.2 they have improved the software's ability to match symbology, fonts, and rendering. Additionally you can now create world files to define the transformation of your data. A tool that seems quite useful is the two-point transformation, which maintains the aspect ratio of the CAD dataset. One can also scale, rotate, and shift a CAD layer to match the extent of an ArcMap layer.
What I would consider the greatest advancement is the capability of the software to translate CAD data into a geodatabase. This allows the user to edit a layer and apply more advanced cartographic representations. Similarly, one is able to convert a modified dataset back to CAD format. I can imagine this is quite useful as well.
Let's see, news from home. Not much exciting. We had a very relaxing weekend, including some hiking at Holmes Experimental State Forest. No quite as scenic as Dupont State Forest, but very solitary and nice. We also learned our apple tree produces Gala apples, so we will be making some apple sauce this week.
Wednesday, August 20, 2008
August 20, 2008
An actual assignment, how unusual. Let's see what I learned today about coverages, shapefiles, and geodatabases.
Coverages were created in the 1970s when GIS were first developed. As a result, many agencies continue to use this data format despite its limitations. The largest drawback is the multi-step process required to create polygons. The user must first individual arc segments, which connect to form a shape, and then he must perform a "build" command to create a polygon. Today, the geodatabase format allows a user to simply draw a polygon and the software creates the necessary data in the associated attribute table. It is a one-step process.
On the other hand, coverages support topology, which is a significant benefit when performing data analysis related to adjacency, connectivity, or containment. A coverage file forces linked nodes and lines to remain connected when editting. Should you change one layer, you must change any associated layers to keep the topology. This is one important function that was lost with the creation of shapefiles.
Shapefiles do not maintain topology, which means the area and perimeter of objects in a layer will not be updated if editting occurs. This is a significant problem for agencies using this format, as the attribute table could provide incorrect data. Despite the speed of shapefiles and the ability to use them in many GIS software programs, the lack of topology functions limit their abilities.
The best of both worlds is the geodatabase, which was introduced by ESRI with their ARCGIS 9.2 update. A geodatabase stores topology, can create polygons without additional commands, and updates the shape of individual features during editting sessions. They are quite useful in the world of GIS and will hopefully become ubiquitous in the near future. Until then, only GIS specialists using ESRIs software have the ability to create this data format.
Coverages were created in the 1970s when GIS were first developed. As a result, many agencies continue to use this data format despite its limitations. The largest drawback is the multi-step process required to create polygons. The user must first individual arc segments, which connect to form a shape, and then he must perform a "build" command to create a polygon. Today, the geodatabase format allows a user to simply draw a polygon and the software creates the necessary data in the associated attribute table. It is a one-step process.
On the other hand, coverages support topology, which is a significant benefit when performing data analysis related to adjacency, connectivity, or containment. A coverage file forces linked nodes and lines to remain connected when editting. Should you change one layer, you must change any associated layers to keep the topology. This is one important function that was lost with the creation of shapefiles.
Shapefiles do not maintain topology, which means the area and perimeter of objects in a layer will not be updated if editting occurs. This is a significant problem for agencies using this format, as the attribute table could provide incorrect data. Despite the speed of shapefiles and the ability to use them in many GIS software programs, the lack of topology functions limit their abilities.
The best of both worlds is the geodatabase, which was introduced by ESRI with their ARCGIS 9.2 update. A geodatabase stores topology, can create polygons without additional commands, and updates the shape of individual features during editting sessions. They are quite useful in the world of GIS and will hopefully become ubiquitous in the near future. Until then, only GIS specialists using ESRIs software have the ability to create this data format.
Monday, August 18, 2008
August 18, 2008
Since Pete bugged us about not updating our blogs during the summer, I thought I would post some of the maps I've created for work. We have the latest and greatest Zoning map, complete with several new parcels and rezonings. There is the potential annexation area to the south of Town, which the Town Council voted down much to my surprise – talk about controversy. A new and improved Greenways map for the Parks and Recreation Department. And finally, an Infrastructure map, with a fun annotation layer of the water lines. If only I could get the sewer district to complete the update of their layer.
I’ve also been working on a building footprints layer, which is extremely tedious. After many days of tracing buildings on the 2001 aerial, I am only 50% complete with the layer. Hopefully I will finish it soon and can think of an exciting class project for it.
While doing some research for Pete's USB connection, I stumbled across this blog about cloud computing, which I thought I would share with the class.
http://www.romow.com/computer-blog/cloud-computing-the-next-big-thing/
I have had a very eventful and stressful summer. It all started off well with a trip to Germany. Then we started remodeling the bathroom early in the summer, which we finally completed in July. A very nice woman let us live with her for a month while they did the work. If only Home Depot hadn’t damaged the tub, life would have been a lot easier. My husband’s father passed away somewhat unexpectedly during the renovations, which just added to our stress. So, I chopped of my hair in hopes a short cut would be easier, which it never is. Maybe I’ll go shorter still….any opinions?
Looking forward to next class Pete.
I’ve also been working on a building footprints layer, which is extremely tedious. After many days of tracing buildings on the 2001 aerial, I am only 50% complete with the layer. Hopefully I will finish it soon and can think of an exciting class project for it.
While doing some research for Pete's USB connection, I stumbled across this blog about cloud computing, which I thought I would share with the class.
http://www.romow.com/computer-blog/cloud-computing-the-next-big-thing/
I have had a very eventful and stressful summer. It all started off well with a trip to Germany. Then we started remodeling the bathroom early in the summer, which we finally completed in July. A very nice woman let us live with her for a month while they did the work. If only Home Depot hadn’t damaged the tub, life would have been a lot easier. My husband’s father passed away somewhat unexpectedly during the renovations, which just added to our stress. So, I chopped of my hair in hopes a short cut would be easier, which it never is. Maybe I’ll go shorter still….any opinions?
Looking forward to next class Pete.
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