Introduction Air Photo Interpretation and Image Mosaicking
Introduction
This assignment there is two parts, which emphasize on Air photo interpretation and Image mosaicking. In Air photo interpretation we will be discussed in all basic elements of air photo interpretation using a chart based on basic elements. For Image mosaicking we have been provided with 6 sheets of small format aerial photos, which cover Indramayu area in West Java that has the purpose to create a RGB image mosaic.
Background
Mosaicking
Mosaicking refers to joining two
or more overlapping images or photos to create a continuous mosaic image. The
mosaic image can be created from difference number of band, difference data
format, or difference resolution of overlapping satellite sensor or aerial
photos to cover a larger geographic area. The image or photo must be the same
coordinate system (Map projection and Geographic datum).
When we have already joined images we could adjust the color of the images by
using the Image Balancing Wizard for Air photos function. This process will be
reduced the difference in brightness and help to balance the contrast between
dataset of mosaic images. And for, Feathering is the process of absorption the
data values in area where two dataset overlap. The visual effect of seam between
mosaic images will be reduced, so that the image will appear to be one
continuous image. The cutlines/stitching line technique uses the region to
assign the preservation area for each image. Usually, the region is created by
head up digitize follow natural earth feature. For the image mosaicking, we can
experiment to integrate all technique to create the best mosaic image for
specific study area.
Air
Photo Interpretation
The aerial photograph represent the feature or phenomena on the ground that various in sizes and shapes. They are a raw photograph data, which should be interpreted become a usable information for most application. There are ten elements of image (air photo) interpretation such as Tone/Color (1st Order Basics), Size, Shape (2nd Order Geometric Arrangement), Texture, Pattern (2nd Order Spatial Arrangement), Site, Association (3rd Order Location Arrangement), Height, Shadow (3rd Order Interpretation) Usually, air photo interpretation will take a simple to the complex interaction of the object on the earth’s surface based on the basic elements of air photo interpretation that following are:
Tone/color is refers to the discrimination of various in brightness or color of the object on aerial photograph. Many factors has effected to the tone or color of air photo such as angle of sun, time of day, film type, filter use, and others. If without the tonal difference, the shapes, patterns, and the textures of object could not be discerned (Lillesand and Kiffer, 1994)
Resolution concern with camera lens, and ground resolution,
that has ability of the entire system to create a sharply defined image.
Size relates to the air photo scale, the consideration of aerial photograph scale should be concerned based on the purpose of the interpretation.
Shape concerns the general form, configuration, or outline of individual object. The specific shape of an object as it is viewed from above (top view) should be known.
Texture is a group of repeated small pattern that depend on the scale of the photograph. However, the texture is also concerned with frequency of change and arrangement of tones.
Pattern refers to the spatial arrangement of objects that is a regular usually repeated shape with respect to an object.
Site is a relation of the object to the topographic location that can help to know the arrangement of the object with respect to one another or to terrain features.
Association is the relationship or context for a specific combination of elements, geographic characteristics, configuration of the surroundings that can provide the user to interpret the specific information, as well as helpful for manmade installation.
Height of the object will provide detail about many
features and useful for analytical studying.
Shadow is usually a visual obstacle for image interpretation. However, shadow can also give height information about tower, tree or tall building, as well as shape information from the non-vertical perspective such as the shape of a bright (Murai, 1993)