ESRI.ArcGIS.ADF.IMS
AcetateElement Class
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ESRI.ArcGIS.ADF.IMS.Display.AcetateElement Namespace : AcetateElement Class




Abstract base class representing an acetate element that can be placed on an acetate layer.

Syntax

Visual Basic (Declaration) 
<SerializableAttribute()>
Public MustInherit Class AcetateElement
Visual Basic (Usage)Copy Code
Dim instance As AcetateElement
C# 
[SerializableAttribute()]
public abstract class AcetateElement

Remarks

Number of features

Acetate layers are designed to show a limited number of graphic features such as a north arrow, scalebar, some text, and one or two points, lines, or polygons. The acetate layer is not designed for displaying large numbers of features. If you add many features to an acetate layer, a noticeable degradation in response time and performance is likely. If too many features are added, the service may stop responding.

If you use the map web controls, you may find that the geometry and graphics classes in ESRI.ArcGIS.ADF.Web provide some equivalent functionality, and provide an alternative to overworking an acetate layer.

Scales

Scales can be set using a relative scale or by calculating the number of map units per pixel. A relative scale represents the scale in a ratio such as 1:24000. In this example, 1 meter equals 24000 meters, or 1 inch equals 24000 inches. When using relative scale, always use a colon (:) between the two values.

Map units per pixel refers to the number of meters, feet, or decimal degrees represented by one pixel in a map. To convert from a relative scale to map units per pixel, the size of a pixel must first be calculated. The formula for finding the number of meters in a pixel is 0.0254 / dpi. The value 0.0254 is the number of meters in an inch, and dpi is the dpi set in the ArcIMS service or request. If no dpi is set in the service or request, the dpi is assumed to be 96. As an example of pixel size, if the dpi is 96, the pixel size is 0.0254 / 96 or 0.000265 m. To convert from a relative scale to map units per pixel:

  • If the scale is in meters. To calculate the number of meters per pixel, take the relative scale and multiply by 0.000265. For example, if the relative scale is 1:24000, then the number of meters per pixel is 24000 * 0.000265, or 6.36 meters.
  • If the scale is in feet. Do the calculation for meters (#1). Multiply the result by 3.28 (the number of feet in a meter). For example, if the number of meters per pixel is 6.36, the number of feet is 6.36 * 3.28, or 20.86 feet.
  • If the scale is in decimal degrees. For these calculations, the Earth is assumed to be an exact sphere with a circumference of 40030.174 km. One degree is 111.195 km (40030.174/360 degrees), or 111195 meters. To calculate the number of degrees, first do the calculation for meters (#1). Next, divide the result by 111195. For example, if the number of meters per pixel is 6.36, the number of degrees is 6.36 / 111195, or 0.0000571968.

Notes for ArcMap image services

When an object is projected on an ArcMap image Service, points and line and polygon vertices will be placed properly when Units are in Database units. However, line segments and polygon edges will be straight rather than projected.

When using ArcMap image services, any scale bar, north arrow, and text objects are always drawn first, before any point, line, or polygon objects.

Inheritance Hierarchy

See Also

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