1. Field of the Invention
The present invention is related to chart display devices, and more particularly to a chart display device for displaying a photograph for land and marine use.
2. Description of the Related Art
When an aerial photograph is overlaid on a chart using typical/conventional methods to obtain an image for use in survey applications, for example, the aerial photograph, the chart, a travel route to a destination and other navigational information on the chart may be displayed in the image. When the travel route on the chart is displayed on the photograph, it may stand out from the aerial photograph depending on how it is displayed. In such a case, information items displayed on the chart, other than the travel route, are difficult to recognize, due to an overload of displayed information.
Disclosed embodiments of this application address these and other issues by displaying an image formed from multiple layers, such as aerial or satellite photograph layers and chart layers associated with land and sea areas, by blending the aerial photographs and the chart with variable transparency values. The transparency values may be obtained based on pixel data associated with one or more layers. Alpha blending technology may be used to obtain transparency values pixels using a depth or altitude database for pixels' depths or altitudes. When a first layer is an aerial or satellite photo and a second layer is a chart, a portion of the photo is provided over a land area, a portion of the chart is provided over a deep sea area, and a blended portion obtained from the photo and the chart is provided in a shallow sea area.