LAYER

Used in

CONFIG  REQUEST  RESPONSE  

Servers

Image  Query  Feature  Extract  Geocode  

Parent elements

GET_EXTRACT  GET_FEATURES  GET_GEOCODE  GET_IMAGE  LAYERS  MAP 

Syntax

<LAYER	Attribute Description Table
When parent element is MAP, GET_IMAGE, GET_EXTRACT:      (r)id="string"      (r)type="featureclass | acetate | image"      maxscale="string"      minscale="string"      name="string"      visible="true | false" [true]      When parent element is LAYERS in a GET_IMAGE request or map configuration file:      (r)id="string"      When parent element is LAYERS in an IMAGE response:      (r)featurecount="string"      (r)id="string"      (r)name="string"      When parent element is GET_FEATURES (referencing an existing layer), GET_GEOCODE:      (r)id="string"      When parent element is GET_FEATURES (Image Service using a dynamic layer):      (r)id="string"      (r)type="featureclass"      When parent element is MAP:      disable_prerender_clipping="true | false" [false]      ignore_scale_for_query="true | false" [false] >      When parent element is MAP, GET_IMAGE, or GET_EXTRACT and LAYER type="featureclass" - Image and Extract Servers:      (r)<DATASET... />      <COORDSYS... />      <DENSIFY... />      <QUERY... /> [Either SPATIALQUERY or QUERY but not both]      <SPATIALQUERY... /> [Either SPATIALQUERY or QUERY but not both]      (m)<EXTENSION... /> [Only valid with MAP]      <GROUPRENDERER... /> [Or]      <SCALEDEPENDENTRENDERER... /> [Or]      <SIMPLELABELRENDERER... /> [Or]      <SIMPLERENDERER... /> [Or]      <VALUEMAPLABELRENDERER... /> [Or]      <VALUEMAPRENDERER... /> [Or]      When parent element is MAP or GET_IMAGE and LAYER type="image":      (r)<DATASET... />      <COORDSYS... />      <IMAGEPROPERTIES... />      <RASTER_RENDERER... /> [Only valid with MAP]      When parent element is MAP or GET_IMAGE and LAYER type="acetate":      (r)(m)<OBJECT... />      When parent element is GET_FEATURES (referencing an existing layer), GET_GEOCODE:           No Child Elements      When parent element is GET_FEATURES (Image Service using a dynamic layer):      (r)<DATASET... />      When parent element is LAYERS:           No Child Elements </LAYER >
(r): Attribute or child element is required. (m):  Child element can be used multiple times.

Description

LAYER can be used in several ways depending on its context:

Parent element is	Description
MAP	Defines a layer used in the service.
GET_IMAGE GET_EXTRACT	Defines an additional layer in the request.
GET_FEATURES	Defines a layer for querying features.
LAYERS in LEGEND	Identifies which layers in a service or request should not be included in the legend.
IMAGE	Returns information on layers in the map including ID, name and number of features.

Restrictions

• ID for each layer must be unique within the service and within any layers added dynamically in a request.
• Use only one renderer at a time.
• Acetate layers are valid only in GET_IMAGE requests. They are not valid in GET_EXTRACT requests.
• EXTENSION and RASTER_RENDERER are valid only when parent element is MAP, and not in a request.

Notes

• Layers can be one of three types:
  
  
  1. featureclass - vector layers that are made up of points, lines, or polygons.
  2. image - raster layers. For a complete list of supported raster formats, see ArcIMS Help.
  3. acetate - graphic objects placed on top of the map such as a north arrow, text, or a point. See OBJECT for more details.
  
  
  The following table lists the valid layer types for requests that use LAYER. MAP is also included since LAYER is an integral part of map configuration files:
  
  

  Parent element is	Supports featureclass	Supports image	Supports acetate
  MAP	Yes	Yes	Yes
  GET_IMAGE	Yes	Yes	Yes
  GET_EXTRACT	Yes	No	No
  GET_FEATURES	Yes	No	No
  GET_GEOCODE	Yes	No	No

  
  
  
• Depending on the request and ArcIMS service type, LAYER can be used to reference existing layers in the service or for adding new layers. In the following table, a service layer is a layer that is included in the service. A dynamic layer is added in the request.
  
  

  Request	Function	Image Service	Feature Service
  GET_IMAGE	Show service layers	Yes	No
  	Include acetate layers (dynamic)	Yes	No
  	Include layers showing selected features (dynamic)	Yes	No
  	Add new featureclass or image layers (dynamic)	Yes	No
  GET_EXTRACT	Extract service layers - featureclass	Yes	No
  	Extract service layers - image	No	No
  	Extract acetate layers (dynamic)	No	No
  	Extract layers showing selected features (dynamic)	Yes	No
  	Extract new layers (dynamic)	Yes	No
  GET_FEATURES	Show service layers	No	Yes
  	Query service layers	Yes	Yes
  	Query dynamic layers	Yes	No
  GET_GEOCODE	Find an address location on a service layer	Yes	No

  
  
  
• In a GET_IMAGE or GET_EXTRACT request, LAYER is used to create a new layer. Use LAYERDEF to change an existing layer's rendering or to turn the layer on or off. For more information about using LAYER in a request, including more examples, see Using GET_IMAGE and IMAGE with Image Services and Using GET_EXTRACT and EXTRACT.
• For ArcSDE layers, DATASET must be defined before renderer.
• Many OBJECTs can be defined in one acetate layer.
• Scales can be set in ArcXML 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 where:
  • The value 0.0254 is the number of meters in an inch.
  • 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 calculating pixel size, if the dpi is 96, the pixel size is 0.0254 / 96 or 0.000265 m.
  
  Once the pixel size is known, the relative scale can be converted to map units per pixel:
  1. If the scale is in meters. To calculate the number of meters per pixel, take the relative scale and multiply by the pixel size (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.
  2. 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 per pixel is 6.36 * 3.28, or 20.86 feet.
  3. 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 per pixel is 6.36 / 111195, or 0.0000571968.

Attribute Descriptions for LAYER

When parent element is MAP, GET_IMAGE, GET_EXTRACT:

Attribute	Usage
id	Unique ID for a layer. The ID can be any combination of alpha and numeric characters. If used in a request to extract data, the characters must be in English and valid for a filename unless the extract EXTENSION for the layer is used.
maxscale	Maximum scale to display map using a relative scale such as 1:24000. Scale can also be calculated as the number of map units per pixel.
minscale	Minimum scale to display map using a relative scale such as 1:24000. Scale can also be calculated as the number of map units per pixel.
name	Layer name. Can be an alias.
type	Specifies layer type. Use "featureclass" for shapefiles and ArcSDE vector layers. Use "image" for raster image files, GRIDs, and ArcSDE raster layers. Use "acetate" for adding graphics on top of the map.
visible	Specifies layer visibility.

When parent element is LAYERS in a GET_IMAGE request or map configuration file:

Attribute	Usage
id	ID as specified in map configuration file or the request. For a legend list to be valid, the ID used must have a match in the map configuration file or the request.

When parent element is LAYERS in an IMAGE response:

Attribute	Usage
featurecount	For shapefile and ArcSDE layers, counts the number of features shown on the map. For image layers, counts the number of images present in the map. For acetate layers, counts the number of times OBJECT is used in a layer.
id	ID as specified in map configuration file or request.
name	Name as specified in map configuration file or request.

When parent element is GET_FEATURES (referencing an existing layer), GET_GEOCODE:

Attribute	Usage
id	ID as specified in map configuration file. For a request to be valid, the ID used in the request must have a match in the map configuration file.

When parent element is GET_FEATURES (Image Service using a dynamic layer):

Attribute	Usage
id	Unique ID for a layer. The ID can be any combination of alpha and numeric characters.
type	Specifies layer type. The only valid value is "featureclass".

When parent element is MAP:

Attribute	Usage
disable_prerender_clipping	When set to "true", features are not clipped to the visible extent. When using ArcSDE layers, in some situations due to the size and complexity of data, performance is slow during GET_IMAGE requests when compared to using shapefile data. In this situation, clipping can be disabled, which may help performance while drawing features. This attribute can only be used in map configuration files when setting up the service.
ignore_scale_for_query	When set to "true", a spatial query works in an image request outside the visible scale range of that layer, and selected features are displayed. When set to "false", selected features cannot be renderered outside the scale. This attribute is valid only when in a map configuration file.

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Examples for LAYER

Example 1: When in CONFIG.

<?xml version="1.0" encoding="UTF-8"?> <ARCXML version="1.1">   <CONFIG>     <ENVIRONMENT>       <LOCALE country="US" language="en" variant="" />       <UIFONT color="0,0,0" name="Arial" size="12" style="regular" />       <SCREEN dpi="96" />     </ENVIRONMENT>     <MAP>       <PROPERTIES>         <ENVELOPE minx="-178.21" miny="18.92" maxx="-66.96" maxy="71.41" name="Initial_Extent" />         <MAPUNITS units="decimal_degrees" />         <FILTERCOORDSYS id="4326" />         <FEATURECOORDSYS id="4326"/>       </PROPERTIES>       <WORKSPACES>         <SHAPEWORKSPACE name="shp_ws-0" directory="<path to USA ESRIDATA>"/>       </WORKSPACES>       <LAYER type="featureclass" name="CITIES" visible="true" id="2">       <DATASET name="CITIES" type="point" workspace="shp_ws-0" />       <SIMPLERENDERER>         <SIMPLEMARKERSYMBOL type="square" width="5" />       </SIMPLERENDERER>       </LAYER>     </MAP>   </CONFIG> </ARCXML>

Example 2: Map configuration file where layers with ID of "0" and "1" are removed from the legend list.

<?xml version="1.0" encoding="UTF-8"?> <ARCXML version="1.1">   <CONFIG>     <ENVIRONMENT>       <LOCALE country="US" language="en" variant="" />       <UIFONT color="0,0,0" name="Arial" size="12" style="regular" />       <SCREEN dpi="96" />     </ENVIRONMENT>     <MAP dynamic="true" >       <PROPERTIES>       <ENVELOPE minx="-180.0" miny="-90.0" maxx="180.0" maxy="90.0" name="Initial_Extent" />       <MAPUNITS units="decimal_degrees" />       <FILTERCOORDSYS id="4326" />       <FEATURECOORDSYS id="4326"/>       <LEGEND title="Legend" font="Arial" autoextend="true" columns="1" width="170" height="300" backgroundcolor="255,255,0" >         <LAYERS>           <LAYER id="0"/>           <LAYER id="1"/>         </LAYERS>       </LEGEND>       </PROPERTIES>       <WORKSPACES>         <SHAPEWORKSPACE name="shp_ws-0" directory="<path to WORLD ESRIDATA>" />         <SHAPEWORKSPACE name="shp_ws-2" directory="<path to USA ESRIDATA>" />         <SHAPEWORKSPACE name="shp_ws-3" directory="<path to CANADA ESRIDATA>" />       </WORKSPACES>       <LAYER type="featureclass" name="WORLD30" visible="true" id="0">         <DATASET name="WORLD30" type="polygon" workspace="shp_ws-0" />         <SIMPLERENDERER>           <SIMPLEPOLYGONSYMBOL filltype="solid" fillcolor="0,153,255" />         </SIMPLERENDERER>       </LAYER>       <LAYER type="featureclass" name="CNTRY94" visible="true" id="1">         <DATASET name="CNTRY94" type="polygon" workspace="shp_ws-0" />         <SIMPLERENDERER>           <SIMPLEPOLYGONSYMBOL filltype="solid" fillcolor="255,255,153" />         </SIMPLERENDERER>       </LAYER>       <LAYER type="featureclass" name="United States" visible="true" id="2">         <DATASET name="STATES" type="polygon" workspace="shp_ws-2" />         <SIMPLERENDERER>           <SIMPLEPOLYGONSYMBOL filltype="solid" fillcolor="255,0,0" />         </SIMPLERENDERER>       </LAYER>       <LAYER type="featureclass" name="Canada" visible="true" id="3">         <DATASET name="province" type="polygon" workspace="shp_ws-3" />         <SIMPLERENDERER>           <SIMPLEPOLYGONSYMBOL filltype="solid" fillcolor="0,153,0" />         </SIMPLERENDERER>       </LAYER>       <LAYER type="featureclass" name="World Cities" visible="true" id="4">         <DATASET name="CITIES" type="point" workspace="shp_ws-0" />         <SIMPLERENDERER>           <SIMPLEMARKERSYMBOL color="102,0,102" width="8.0" />         </SIMPLERENDERER>       </LAYER>     </MAP>   </CONFIG> </ARCXML>

Example 3: When used with LAYERS to remove layers with ID of "0" and "1" from the legend list.

<?xml version="1.0" encoding="UTF-8"?> <ARCXML version="1.1">   <REQUEST>     <GET_IMAGE>       <PROPERTIES>         <LEGEND title="Legend" font="Arial" autoextend="true" columns="1" width="170" height="300" backgroundcolor="255,255,0" >           <LAYERS>             <LAYER id="0"/>             <LAYER id="1"/>           </LAYERS>         </LEGEND>         <DRAW map="false"/>       </PROPERTIES>     </GET_IMAGE>   </REQUEST> </ARCXML>

Example 4: Identifying a layer by its ID in a GET_FEATURES request.

<?xml version="1.0" encoding="UTF-8"?> <ARCXML version="1.1"> <REQUEST>   <GET_FEATURES featurelimit="25" beginrecord="0" outputmode="xml" geometry="false" envelope="true" compact="true">     <LAYER id="4" />     <SPATIALQUERY subfields="#ALL#" where="NAME  =  'Los Angeles'" >     </SPATIALQUERY>   </GET_FEATURES> </REQUEST> </ARCXML>

Example 5: When DATASET is used as a child element of a dynamic layer in a GET_FEATUREs request. (Valid with Image Services only)

<?xml version="1.0" encoding="UTF-8" ?> <ARCXML version="1.1">   <REQUEST>     <GET_FEATURES featurelimit="5" beginrecord="0" outputmode="xml" geometry="false" envelope="true">       <LAYER id="40" type="featureclass" >         <DATASET name="country" type="polygon" workspace="shp_ws-0" />       </LAYER>       <SPATIALQUERY subfields="#ALL#" where="POP_CNTRY &gt; 100000000" />     </GET_FEATURES>   </REQUEST> </ARCXML>

Example 6: IMAGE response showing details on layers in the requested ArcIMS service.

<?xml version="1.0" encoding="UTF8"?>   <ARCXML version="1.1">     <RESPONSE>       <IMAGE>         <ENVELOPE minx="-180" miny="-135" maxx="180" maxy="135" />         <LAYERS>           <LAYER name="CNTRY94" id="0" featurecount="165" />           <LAYER name="STATES" id="1" featurecount="51" />           <LAYER name="province" id="2" featurecount="12" />         </LAYERS>         <OUTPUT file="c:\arcims\output\world_MYCOMPUTER3633699.jpg" url="http://mycomputer.domain.com/output/world_MYCOMPUTER3633699.jpg" />       </IMAGE>     </RESPONSE>   </ARCXML>

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