| 作成者 |
|
|
|
|
|
|
|
|
|
| 本文言語 |
|
| 出版者 |
|
|
|
| 発行日 |
|
| 収録物名 |
|
| 巻 |
|
| 開始ページ |
|
| 終了ページ |
|
| 出版タイプ |
|
| アクセス権 |
|
| JaLC DOI |
|
| 概要 |
パソコン上で作動するGISソフト(アメリカmicroimages社製 TNTmips)を用いて,3種類の作成方法でデジタルオルソフォトを作成し,その精度を比較した.2枚1組のステレオペア写真から発生させた数値地形図(Digital Elevation Model: DEM)を用いてオルソフォトを作成する方法1,既存している等高線をデジタイズしたベクターデータから作成したDEMを用いて作成する方法2...,市販の数値地図50mメッシュ(標高)を用いて作成する方法3について,それぞれオルソフォトを作成した.作成したオルソフォトの精度を測定した結果,方法1の精度が最も良く,ついで方法2,3の順であった.また作成に関する手順や作業量について比較すると,方法2および3に比べ方法1が格段に手順も多く作業量も大きかった.これらの労力と作成されたデジタルオルソフォトの精度を考慮すると,方法3の作成法を用いてデジタルオルソフォトを作成することが最も効率的であると考えられた.次にGCP点数を7,68,96,237,327および365点と変えて作成したオルソフォトについては,GCP点数が多いほど精度が良くなるといった正の相関関係は見いだされなかったが,GCPがオルソフォトの精度に大きな影響を及ぼしていると考えられた.また作成したオルソフォトの精度を正確に評価することが難しいことが考察された.
Photogrammetry and photointerpretation have been developed previously. However, all aerial photographs contain systematic distortion caused by camera angle, distance and surface elevation. As a result, their internal geometry differs from the ideal geometry, and they are therefore limited to use in geospatial analysis. Orthophotographs have map-like geometry and are useful as an accurate image base for geospatial analysis. Although orthophotographs are useful, creating orthophotographs has previously been very expensive and has required professional knowledge, advanced techniques and special machines, so orthophotographs have not been widely used yet. Recently, however, GIS software that runs on personal computers and can create digital orthophotographs has become available. TNTmips is one such software program. In this paper, we present a procedure for creating digital orthophotographs on TNTmips and report their accuracy. Because aerial photographs distortion results from camera angle, distance and surface elevation, orthophotographs must be compensated for these factors. A digital elevation model (DEM) provides surface elevation information, so we used several types of DEMs to compare accuracy of digital orthophotographs derived from them. There are three types of DEMs. The first is a DEM created from a pair stereo aerial photographs (Method-1). The second is a DEM created from a digital line graph (Method-2). The third is a DEM published by the Geographic Survey Institute (Method-3). To compare the accuracy of these orthohphotographs, we calculated the difference between the measured value and at some points and determined the residual of the GCP. In comparing the accuracies of these three methods, we found that the best method is Method-1 and the worst one is Method-3. It was too costly to make orthophotographs by Method-1, so we recommended Method-3. In addition to comparing the accuracy of orthophotographs derived from different DEMs, we also compared the accuracy of orthophotographs with differing GCP values. As a result, we found that the accuracy of orthophotographs increased with increasing GCP up to a point but was not affected beyond that point. We also found that evaluating the accuracy of orthophotographs was too difficult because the calculated accuracy was strongly affected by GCP positions.続きを見る
|
Mendeley出力
