Digital Image Processing Tutorial-Image Interpretation Part-II

Image interpretation

The main objective of image interpretation is to create information in the form of thematic maps.

A thematic map can be prepared by categorizing all pixels of the image into classes or themes to generate map from the remote sensing data.

• One can take different theme based on field of study, for example one can create
• Landuse/land cover map based on mapping different categories such as water, forest, rangeland, urban etc.
• Mapping and quantification of surface water bodies/ water resources.
• Geological map based on identification of landforms, rock types, folds, faults and fractures.
• Urban change detection maps using multi date remote sensing data.

Below steps followed for Image Interpretation-

Classification

               Assign objects to classes

               Detection, recognition, identification.

               Interpreter confidence is ranked as possible, probable

Measurement

              Uses image scale to derive measurements such as length with distance and volume

Delineation

              Demarcation of regions

ThematicMap

              Conversion of information into the thematic maps

To start and understand process of image interpretation, it is essential to understand elements/key of image interpretation. These elements help expertise/user to interpret objects in better way both qualitative and quantitative.

An image interpretation is process which includes image reading, image measurement and image analysis. 

• Image reading corresponds to simply identification of objects on satellite image using elements/keys of image interpretation. 
• Image measurements include extraction of quantitative properties such as length, location, height, density etc from satellite images.
• Image analysis, involves comparative analysis of interpreted information to actual phenomenon of satellite image/ground and also evaluate the condition of objects on the satellite image.

The outcome of image reading, image measurement and image analysis will be a interpreted map, which may be representing a specific theme.

Elements/Keys of image interpretation

During image interpretation, numbers of characteristics are employed to detect and identify object on satellite image/aerial photographs. Usually in our daily life exposure to earth surface object can help to identify objects. Based on personal experience about earth surface feature such as size, shape, color etc can facilitate user to understand, identify and recognize objects both in qualitative and quantitative way. Identifying objects using these image elements on remotely sensed images (Satellite Image/Aerial Photographs) can facilitate user to further interpret and analyze.

Image analysis requires explicit recognition of nine elements of image interpretation that form the framework and understanding of an image

1. Size
2. Shape
3. Shadow
4. Tone/Color
5. Texture
6. Pattern
7. Height & depth
8. Site/Situation
9. Association

The above elements/keys of image interpretation used for identification and recognize of objects on remote sensing data.

These elements will be discussed in detail in next article.