RealScape-Metropolitan Fixed Assets Change Judgment by Pixel-by-Pixel Stereo Processing of Aerial Photographs

By Koizumi, Hirokazu; Yagyu, Hiroyuki et al. | AI Magazine, Spring 2010 | Go to article overview
Save to active project

RealScape-Metropolitan Fixed Assets Change Judgment by Pixel-by-Pixel Stereo Processing of Aerial Photographs

Koizumi, Hirokazu, Yagyu, Hiroyuki, Hashizume, Kazuaki, Kamiya, Toshiyuki, Kunieda, Kazuo, Shimazu, Hideo, AI Magazine

This article describes the Fixed Assets Change Judgment (FACJ) system and its core tool, RealScape. RealScape automatically detects changes in the height and color of buildings based on three-dimensional analysis of aerial photographs. The three-dimensional analysis employs a pixel-by-pixel stereo processing method that calculates the height of each pixel in aerial photographs and thus enables precise difference detection between previous and current aerial photographs. The FACJ system reduces the labor costs to one third of the traditional approach and the required judgment duration to about two weeks per 100 k[m.sup.2]. The FACJ system was experimentally used by the Tokyo Metropolitan Government for the first time in 2005. Since then, it has been used at its tax bureau every year to calculate the municipality's fixed-asset tax. After the success in Tokyo, other major city governments, including Osaka and Sapporo, have followed suit.

Problem Description

The Japanese fixed-property tax is imposed by municipalities on the owners of land, buildings, and depreciation assets (all hereinafter referred to as "fixed assets") on January 1 of every year by calculating the tax sum according to current asset values. For this purpose, the municipalities take aerial photographs every year on January 1 and compare the photographs with those of the previous year to identify building-change information (new construction, loss, enlargement, reform, reconstruction, work in-progress, and so on). The identification of such changes is entrusted to survey companies who hire a large number of workers (figure 1, left). However, reliance on human labor has led to problems detailed in the following paragraphs.


Huge Costs, and the Impossibility of Eliminating Human Judgment Errors

It takes about 10 hours to read and interpret a single photograph, and the average municipality must perform this work for several hundred photographs. In addition, errors are not acceptable from the viewpoint of fair taxation, in particular, oversights in finding actual changes to buildings. Nevertheless, the current work done using the traditional system is dependent on the capabilities of individuals, so errors are unavoidable. In addition, in visual-identification work, attempts to prevent oversight errors are made by performing several read operations per area (figure 2), but this leads to a further increase in cost. Every photograph is taken over a scale that can cover an actual area of 800 by 600 meters or 500 by 600 meters (variable depending on the municipality), and every municipality has several hundred photographs that must be read. As a result, it is not rare for the person-hours required for the photograph-reading operation to exceed 10,000.

Under these circumstances, the incentives for the municipalities to overcome such challenges by automating or systematizing the photograph-reading work are now higher than ever. The criteria for the identification of changes are based on laws and guidelines issued by the Research Center for Property Assessment System. Specifically, the criteria are designed to detect height changes of 2 meters or more in an area of approximately 2 by 2 meters, and color changes in an area of approximately 2 by 2 meters. In other words, these criteria require the detection of any change in an area over 2 by 2 meters. Since these requirements set such a high hurdle for achieving automatic processing, the attempts made to automate this work have so far been limited to use of a few specific tools, and the available technology is still far from real systematization. The automation of this work involves the following problems.


Height and Color Change Detection

The height information may be obtained by aerial surveys using a laser profiler, but the laser profiler does not satisfy the area requirement because its resolution is too sparse to satisfy this requirement in normal use.

The rest of this article is only available to active members of Questia

Sign up now for a free, 1-day trial and receive full access to:

  • Questia's entire collection
  • Automatic bibliography creation
  • More helpful research tools like notes, citations, and highlights
  • Ad-free environment

Already a member? Log in now.

Notes for this article

Add a new note
If you are trying to select text to create highlights or citations, remember that you must now click or tap on the first word, and then click or tap on the last word.
Loading One moment ...
Project items
Cite this article

Cited article

Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

Cited article

RealScape-Metropolitan Fixed Assets Change Judgment by Pixel-by-Pixel Stereo Processing of Aerial Photographs


Text size Smaller Larger
Search within

Search within this article

Look up

Look up a word

  • Dictionary
  • Thesaurus
Please submit a word or phrase above.
Print this page

Print this page

Why can't I print more than one page at a time?

While we understand printed pages are helpful to our users, this limitation is necessary to help protect our publishers' copyrighted material and prevent its unlawful distribution. We are sorry for any inconvenience.
Full screen

matching results for page

Cited passage

Citations are available only to our active members.
Sign up now to cite pages or passages in MLA, APA and Chicago citation styles.

Cited passage

Welcome to the new Questia Reader

The Questia Reader has been updated to provide you with an even better online reading experience.  It is now 100% Responsive, which means you can read our books and articles on any sized device you wish.  All of your favorite tools like notes, highlights, and citations are still here, but the way you select text has been updated to be easier to use, especially on touchscreen devices.  Here's how:

1. Click or tap the first word you want to select.
2. Click or tap the last word you want to select.

OK, got it!

Thanks for trying Questia!

Please continue trying out our research tools, but please note, full functionality is available only to our active members.

Your work will be lost once you leave this Web page.

For full access in an ad-free environment, sign up now for a FREE, 1-day trial.

Already a member? Log in now.

Are you sure you want to delete this highlight?