Beware the faults

Written March 20th, 2015 by

Tilted HouseThe Digital Cadastral DataBase (DCDB) can be utilised to give you the number of units in building covered by group title. The cadastre can identify the common property, normally “Lot 0”, and each individual unit in the building, including the unit area and external shape. This is very useful when you have multiple floors in a building and the aerial photography or satellite view make it very difficult to identify the number of floors and number of units per floor in that building.

This method is not always reliable. We have found faults in the DCDB, when a group title property contains more than one building, that you need to be aware of. In locations were there are two or more buildings, we have seen instances of every unit “lot” within the property being assigned across multiple buildings. Let me give you an example to explain this. Read the rest of this entry »

Weather and urban growth modelling

Written September 2nd, 2014 by

Gavin Schmidt presenting at TEDI came across this TED talk by Gavin Schmidt. He is a NASA climate expert and his presentation was about weather models and climate models. In his talk, Gavin explains why we can be confident about predicting how the climate will react into the long-term future.

He discusses the enormous complexities of modelling climate patterns that span a range of 14 orders of magnitude across both time and space. I though modelling urban growth was complex! We are only dealing with 2 orders of magnitude. Even at that level, there is a large body of work required to build and test an urban growth model. I certainly appreciate the mammoth effort needed to build climate models at those scales of magnitude and complexity. Read the rest of this entry »

How to establish a baseline

Written July 7th, 2014 by

Baseline image

The baseline is the most important element of an urban growth model.  Actually, this statement applies to any model. The baseline establishes the reference point from which a model will forecast future growth.  Not having an accurate baseline will result in your model either over or under allocating urban growth, especially in the early projection year cohorts.

Normally your baseline can be derived from the existing land uses of cadastral land parcels within the area that is subject to the urban growth model.  You might think establishing a baseline for a large cadastral model is a very challenging task.  Actually with today’s digital geospatial tools it is relatively easy. Although it is still time-consuming.

So how do you go about creating a baseline? Read the rest of this entry »