Analysis of the whole process of common tilt data processing in SuperMap idesktop

author ： Jiang er

Catalog

Overview of tilt data

Pre processing of tilt data

Great Xinjiang wisdom map

Product docking instructions

Operation flow of 3D model reconstruction

XML Document output

iDesktop Conventional tilt data processing

Generate configuration files

Operation steps

matters needing attention

Basic data issues

Inclined warehousing

Operation steps

Parameters,

matters needing attention

WebGL front end

Load tilt mode

Optimize loading

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Overview of tilt data

Tilt photography （oblique image） It refers to the image obtained by an aerial camera with a certain tilt angle . Tilt photography is a new and high technology developed in the field of international surveying and remote sensing in recent years , By carrying multiple sensors on the same flight platform , At the same time, from the vertical 、 Collect images from different angles such as tilt , Get more complete information about ground objects .

Aerial tilt images can not only truly reflect the situation of ground objects , But also through the use of advanced positioning technology , Embed accurate geographic information 、 Richer image information 、 More advanced user experience , It has greatly expanded the application field of remote sensing images . This technology can be widely used in emergency command 、 Homeland security 、 city management 、 Real estate tax and other fields .

SuperMap iDesktop The function of pre-processing tilt data is not provided in , Therefore, it is recommended that before using in the software , First, conduct preliminary data processing in the third-party software , Such as the wisdom map of Xinjiang 、CC Such as software , After confirming that the basic data is correct, carry out subsequent processing .

Pre processing of tilt data

Great Xinjiang wisdom map

Product docking instructions

There are six models of Dajiang software output in terms of achievement format OSGB\PLY\B3DM\OBJ\S3MB\I3S. among ,OSGB、OBJ、S3MB Equiform ,SuperMap iDesktop The product can support subsequent tilt data processing and publishing . It is usually recommended to OSGB The format is imported from the big Xinjiang intelligence map , For subsequent processing 、 Put in storage 、 And front-end calls ; With S3MB The tilt exported from the format can be directly docked Supermap product , for example iDektop This is not recommended , This is because iDesktop The product can use the tilting warehousing function , take osgb Format conversion to S3MB Format , The tilt data is optimized through parameter setting , Help to improve front-end performance .

Operation flow of 3D model reconstruction

The following steps are the common tilting process , There are six steps , Please refer to the detailed description of the software for detailed steps .

1. A new task - Three dimensional model

;

2. Import image

;

3. Parameter setting - Define the coordinate system

;

4. Air three processing - Like a control point

;

5. Determine the scope of modeling

;

6. Three dimensional modeling .

XML Document output

When Dajiang Zhitu software produces inclined data, it will output at the same time metadata.xml file , It contains tilt coordinate system and position information ,XML Documents cannot be produced separately . because iDesktop The tilt data generation configuration file in requires XML File as metadata , Therefore, it is suggested that the output should be metadata.xml Metadata is properly retained and backed up .

iDesktop Conventional tilt data processing

The conventional processing of tilt data is divided into two steps : Generate configuration files 、 Inclined warehousing . The data after warehousing can be published , And subsequent front-end call data and other operations , Here we will not introduce non idesktop Platform tilt treatment .

Generate configuration files

Operation steps

1. The following example is in iDesktop Official website 10.2.1 Version . stay idesktop Find 3D data in the function bar - Generate configuration files

2. In the generate tilt profile dialog , Set source path , Root node folder , As shown in the figure below Model Is the root node folder . The metadata is generated simultaneously by slanted data metadata.xml Folder , To read the tilted original coordinate system, for example EPSG32649 Projection coordinate system , And model reference points XYZ Coordinate value . For example, the configuration file generated by tilting appears fuzzy , Please consider whether to output for the new version of Dajiang Zhitu osgb, At the same time, confirm whether to remove the outermost layer model.osgb Then generate the configuration file , And browse again .

3. After confirming to generate the configuration file , If the target path defaults to , In the root directory （Model Folder ） Profile found in （config.scp file ）, As shown in the figure . If there are multiple tiles The root directory of the folder contains all tiles The outer folder of .

4. Add the configuration file to the scene to browse , Right click the scene - New spherical scene - Layer manager - Normal layers - Add a 3D slice cache layer , Select profile （config.scp） The location of . After adding layers , Double click to locate the tilt position .

matters needing attention

1. Projection settings 、 Model reference point , Read from metadata.xml file , For example, it is found that the tilt data cannot be located in the scene , Can check metadata.xml Whether the file is matched with the tilt data , And whether the reference point unit is consistent with the coordinate system unit .

2. If not metadata.xml The document needs to be confirmed after tilting the original data coordinate system , Then projection sets the original coordinate system of tilt data .

3. If the tilt origin coordinate system is ENU, Note that the coordinate unit is degrees , It is emphasized that the default unit setting for slanted warehousing is meter, which needs to be changed to degree .

Basic data issues

The output software version update affects

Here is an example to compare the output data of the new and old versions of Dajiang Zhitu （3.1 Left VS3.4 Right ） , Great Xinjiang wisdom map 3.4 The version will generate three more rough layers , You need to move the root node directory before generating the configuration file , Those with many levels are new versions , What is less hierarchical is the old version ）.

Inclined warehousing

Operation steps

Parameters,

1. Parameter setting ：

S3M Version is divided into S3M1.0/2.0, If you are using 10.21 Previous WebGL package （SuperMap iClient3D） Load tilt cache file , It is recommended to use S3M1.0 ;S3M2.0 Is characterized by support for PBR texture of material .

The storage types are divided into original 、 compact , Encrypt tilt data , The storage type must be compact ; Tilt data is stored in MongoDB in , The storage type must be original .

The time required for geometric compression is ： Uncompressed < General compression <Draco Compress . The texture compression format supports five compression formats ：WebP（PC/ Mobile , Minimum amount of data , Memory consumption , Items that do not occupy memory are recommended ）、DXT（PC, Good rendering performance , The total amount of data increases , The project takes up a lot of memory. It is recommended that DXT Format +CRN-DXT5 Loading efficiency is very fast ）、CRN_DXT5（PC equipment ）、 standard CRN、 KTX2.0, Data processing time CRN_DXT5< standard CRN< KTX2.0, The default is DXT（PC equipment ）.

The coordinate unit of the center point is the coordinate system unit set by the projection when generating the configuration file , Usually the projection coordinate system is in meters ,ENU Coordinate system here is degree .

Texture remapping is used to solve the problem of unreasonable texture stitching in partial skew data , Lifting performance , Not checked by default .

2. normal ： The algorithm type can be set 、 Included angle threshold parameter , When there are problems in browsing the data after warehousing, and there are other problems , It can be adjusted through this parameter setting .

3. Merge the root node ： When the model space is wide 、 The amount of data is huge , The model is divided into many root nodes , It takes a long time to read these root nodes, resulting in slow loading of the model , here , You need to merge root nodes to improve loading efficiency .“ Merge the root node ” The function is to merge the root nodes in a certain adjacent space into one root node , That is, a coarser layer of LOD Hierarchy . When the pyramid level is 1 when , For each 4 The root nodes are merged into 1 individual , Every merge , The number of root nodes of the model is reduced to about... Of the original number 1/4. The system will control the final number of root nodes of the model , Ensure that the root node is in 10 Within a . When more than 10 Time , Will continue to merge , Until 10 Within a . This applies when the model space is wide 、 Large amount of data , So that the model is divided into many root nodes , The long time it takes to read the root node will cause the load to be slow , Therefore, it is necessary to merge root nodes to improve loading efficiency . In addition to tilting the data merge root node, it is also suitable for fine model caching , A precision model is a model with extremely high precision , In terms of general modeling , A model without control over the number of faces is a fine model , Generally speaking, all tetrahedral structures 、 modelling 、 doors and windows 、 Objects, etc. are built in proportion . You can refer to iDesktop About... In the help document ” Merge the root node “ as well as ” Model cache merge root node “ And so on . Help documents are available on the official website  （http://support.supermap.com.cn/product/iDesktop.aspx） in ’ Online Help ‘ Lateral ” download “ Can be found in .

4. Model monomer ： Set the data source of the vector plane superimposed on the model 、 Data sets and target fields , The vector surface is usually a two-dimensional surface drawn by itself , The target field is the unique identifier of the vector surface monomer .

5. Set the target coordinate system ： If the original coordinate system is ENU, The coordinates are in degrees , In the new version, the coordinate unit of the center point shall be set as degrees , The corresponding target coordinate system is EPSG4326; For example, both the original coordinate system and the target coordinate system are local coordinate systems , You need to set the projection conversion parameters , This parameter is usually kept by the local surveying and Mapping Bureau ; For example, the original coordinate is the projection coordinate system , The coordinate units are set to meters , The new version needs to set the target coordinate system to the corresponding geographic coordinate system , Examples of corresponding coordinate systems ：

Projection coordinate system （EPSG Code ）	Geographic coordinate system （EPSG Code ）
WGS_1984/Web_Mercator （3857）	GCS_WGS 1984 （4326）
3Degree GK Zone 35     (CGCS2000)（4523）	GCS_China_2000 （4490）
Xian_1980_3_DEGREE_GK_Zone_45N（2390）	Xi-An 1980 China（4610）
GK Zone 14     (Beijing 1954)（21414）	Beijing 1954（4214）

matters needing attention

1. The new version 10.2.x After the iDesktop, The target coordinate system should be set as the geographic coordinate system corresponding to the original tilt data coordinate system when the tilt data is stored . This operation is to fix that the default coordinate system of the old version is all changed to EPSG4326 The error caused .

2. Handle tilted S3MB File note file size , If exceeded 5MB, Then it is unreasonable to merge the root node , You need to adjust the parameter settings of the merge root node . After warehousing combine.scp The file can no longer be adjusted for the merge root node , Only re receipt adjustment is allowed .

WebGL front end

Load tilt mode

WebGL There are generally two ways to load the cache in :

1.scene.open： Use this interface to load url , May refer to SuperMap Official website example BIM Model (http://support.supermap.com.cn:8090/webgl/examples/webgl/editor.html#S3MTiles_BIM) Source code No 104 That's ok ：

for example ：

var promise = scene.open("http://www.supermapol.com/realspace/services/3D-BIMbuilding/rest/realspace");

2.scene.addS3MTilesLayerByScp： load url Please refer to the official website for examples of dynamic monomer (http://support.supermap.com.cn:8090/webgl/examples/webgl/editor.html#dynamicDTH) Source code No 56 Line ：

for example ：

var promise = scene.addS3MTilesLayerByScp('http://www.supermapol.com/realspace/services/3D-dynamicDTH/rest/realspace/datas/Config%20-%201/config', {

name: 'oblique photography'

});

Optimize loading

1.Layer.indexedDBSetting.isGeoTilesSave = true, Optimize loading , The browser crashes easily after opening , But if the computer is not good enough , Will cause the browser to crash . Generally not recommended .

2.S3MTilesLayer.clearMemoryImmediately =false, Not releasing memory in time , Let the model not reload .

3. Open spatial index , Use the new version 10.2.X as well as 11i Series of iDesktop Slant warehousing will automatically create spatial indexes without manual creation . The front end needs to add some code to read the spatial index . for example ：

var layer = scene.layers.find('Config');

layer._maxSkipNum = 256;

layer.LoadingPriority =Cesium.LoadingPriorityMode.UsePagedLodInfo;