Precautions for Vector Tile Cartography

1. Layer Data Content

2. Layer Properties Settings

3. Thematic Maps

4. Text Style

5. Point Symbols

6. Line Symbols

7. Fill Symbols

8. Map Properties Settings

9. Vector Tile Generation Configuration

10. Vector Tile Update

This article summarizes the SuperMap map styles and settings that SuperMap vector tiles can and cannot support, defines clear capability boundaries, and assists users in creating vector maps suitable for vector tile production.

SuperMap supports generating vector tiles (.mvt) that follow the MapBox MVT specification from vector maps. Tile data includes the geometry and attributes of features, while the styling of features is described by a MapBox standard style file (style.json) and follows the style specification of MapBox GL version 8. For more information on MapBox styles, please refer to: https://www.mapbox.com/mapbox-gl-style-spec.

The vector tiles generated by SuperMap will be displayed in SuperMap iClient based on the MapBox style file; the client uses MapBox GL or OpenLayers to render vector tiles. Among them, OpenLayers supports rendering vector tiles in various projections, while MapBox GL only supports rendering vector tiles in the EPSG:3857 projection.

When generating vector tiles, the program needs to translate SuperMap's map styles into MapBox style descriptions. However, some of SuperMap's map styles and settings are not supported by MapBox and cannot be translated into MapBox style descriptions. Therefore, after generating vector tiles from a SuperMap map, the display effects may be inconsistent with the original map, or some style and map setting effects may be lost.

Map Content, Rendering Styles, and Related Configuration		Supported by Vector Tiles	Remarks
1. Layer Data Content
Vector Dataset	2D point, line, region, text datasets	Supported	Raster data layers are not supported. When a map contains unsupported dataset layers, these layers will be ignored during vector tile generation. If a geometry contains too many sub-objects, it will affect the tile generation speed when creating vector tiles. It is recommended to split the sub-objects to improve tile generation efficiency. The styles of EPS data layers in the map cannot be converted to vector tile style descriptions, meaning the styles cannot be output.
	3D point, line, region, text datasets	Supported
	Tsinghua Sunrise (EPS) point, line, region, text datasets	Partially Supported
	Other Datasets	Not Supported
Geometry Complexity			For massive region data, to improve vector tile generation and display efficiency, data simplification is required. Whether to apply simplification can be set by the user based on the actual data. For data sources other than PostGIS, simplification during vector tile generation is specified by the "Rarefy Display" parameter. Checking this option means simplification is applied; otherwise, it is not. For PostGIS data sources, it is necessary to modify the SuperMap.xml file (located in the SuperMap iDesktopX installation directory/BIn/) and add the "<MVTSimplifyPGIS>TRUE</MVTSimplifyPGIS>" tag. The default parameter value is TRUE, indicating simplification; FALSE indicates no simplification. For area objects with dense nodes and complex shapes, at small scales, after simplification, the resulting vector tiles may have deformed area objects, for example: A river represented as an area at a small scale becomes significantly deformed after simplification. It is recommended that users, during cartography, ensure the map has reasonable complexity at different display scales. Here, it is suggested to use line objects to represent rivers at small scales. For tens of millions of land polygon data, after simplification, at small scales, the deformation of area objects may cause hollow areas in the map. It is recommended to first create a vector pyramid for massive land polygon data, and then generate vector tiles.
Vector Data Coordinate System			If the coordinate system of the data is different from the map's display coordinate system, during vector tile generation, the system will perform a coordinate system transformation on the data, converting it to the map's display coordinate system. If the map data volume is large, this transformation operation will consume significant disk space and tile generation time. It is recommended that users first transform the data's coordinate system to the map's display coordinate system, and then generate vector tiles.
2. Layer Properties Settings
Layer Visible Scales	Maximum, minimum visible scale	Supported	Vector tiles are created using global scales. The visible scale range of layers in the vector map needs to be adjusted according to the global scales; otherwise, the visibility effect of map elements in the vector tiles may be inconsistent with the original map. The numerical values and precision of layer visible scales must exactly match the global scales.
Layer Display Filter	Filter expression	Partially Supported	When "Separate data from style" is checked during vector tile generation: Only simple logical relationship judgments and comparison operations are supported. Comparison operations support =, <, >, !=. Values participating in expression comparisons only support numbers; text or characters are not currently supported, i.e., expressions like "NAME = 'Sichuan Province'" are not supported. Logical relationship judgments: Support And, Or, Not Field names in filter expressions cannot be prefixed with table names, i.e., expressions with table names like "China_Province.pop_2014 > 3833" are not supported. When the filter expressions used for point labels and their corresponding layers (thematic maps and normal layers) are different, the resulting vector tiles will use the label's filter expression. When "Separate data from style" is NOT checked during vector tile generation: Layer display filters are supported without restrictions. When outputting vector tiles, only data matching the conditions will be output to the tile data, effectively reducing tile volume.
Layer Join Attribute Table Settings		Not Supported
Normal Layer and Thematic Layer Aggregation			In the same map, for the same point/line/region dataset, at most one thematic map and one label thematic map based on that point/line/region dataset are supported to exist simultaneously; otherwise, unexpected results may occur. However, this restriction is invalid when the display filter results of multiple label thematic maps do not intersect. In the same map, for the same point dataset, at most one unique value thematic map and one single-value label thematic map based on that point dataset are supported to exist simultaneously, and both must use the same field for their single-value fields. Alternative Solution: If a point/line/region dataset requires multiple thematic maps, layer groups can be used for separation: create multiple layer groups, ensuring that within each layer group, for the same point/line/region dataset, it contains at most one thematic map and one label thematic map based on that dataset; within the same layer group, for the same point dataset, at most one unique value thematic map and one single-value label thematic map are supported simultaneously, and both must use the same field for their single-value fields. Labels and their corresponding vector layer need to be under the same layer group, and the label layer should be placed above the corresponding vector layer.
Object Minimum Size		Supported
Layer Blend Mode		Not Supported
Scale With Map		Not Supported
Weight		Not Supported
Rarefy Display Settings		Not Supported
Filter Small Overlapping Objects Settings		Not Supported
Object Display Order		Not Supported
3. Thematic Maps
Unique Value Thematic Map	Single Value Expression	Partially Supported	Only supports a single field; does not support field expressions or SQL function calculation results, e.g., name \|\| '_'\|\| type. Note: Vector tiles do not display sub-item objects with a field value of NULL.
	Property Field Defining Marker Style	Partially Supported	Version 12.0.0 and above, only supports point unique value thematic maps controlling symbol rotation angle via fields. Apart from this, controlling symbols, color, size, or rotation angle via property fields is not supported.
	Thematic Layer Offset Settings	Not Supported
	Marker Style	Partially Supported	For support details, refer to the "Point Symbols," "Line Symbols," and "Fill Symbols" sections.
	Traffic Situation Configuration	Not Supported
Graduated Color Thematic Map	Segmentation Expression	Supported	Currently only supports a single field; does not support field expressions or SQL function calculation results.
	Segmentation Method	Supported
	Segment Precision	Supported
	Marker Style	Partially Supported	For support details, refer to the "Point Symbols," "Line Symbols," and "Fill Symbols" sections.
Uniform Label Thematic Map	Label Expression	Partially Supported	For the labeling fields used by label thematic maps, currently only a single field is supported; field expressions and SQL function calculation results are not supported, e.g., name \|\| '_'\|\| type.
	Label Background	Partially Supported	Background Shape: Supports rectangle, rounded rectangle, point symbol; does not support diamond, ellipse, triangle. Background Style: Only supports pure filling; rounded rectangle background supports setting a fill outline; rectangle does not. Background Margin: Supported Background Shadow Effect: Not Supported For the same point dataset, when both a point normal layer and a label thematic map based on that layer exist simultaneously, MapBox does not support setting both a point symbol and a label background; otherwise, the point symbol will be lost, and although the label remains, the label background will deviate from the label text. When a point symbol is used for the label background, the point symbol does not automatically adjust its size based on the label length.
	Label Offset	Supported
	Leader Line	Not Supported
	Label Alignment with Point	Partially Supported	Left baseline, right baseline, and central baseline alignment are not supported.
	Overlap and Avoidance Settings (Flow, No Overlap)	Not Supported	MapBox handles the avoidance of map elements differently from SuperMap, leading to differences in the number of labels displayed, label alignment with points, etc., between the two.
	Text Layout (Long Text Handling, Line Break, Multi-Line Text Alignment, Landscape Display Tags)	Not Supported	MapBox handles line breaks for long labels differently from SuperMap. When label thematic maps use settings related to label line breaks and multi-line text layout, the display effects in the generated vector tiles may differ significantly from the original map.
	Text Avoidance of Tile Range	Not Supported (Supported in version 12.0.1 and above)
	Label Height Range	Not Supported
	Text Style Settings	Partially Supported	For support details, refer to the "Text Style" section.
	Label Along-Line Orientation	Partially Supported	MapBox styles only support two along-line orientations (perpendicular to the line and top-to-bottom, left-to-right). If the map sets other along-line orientations, the vector tile will use the "top-to-bottom, left-to-right" orientation for label placement.
	Show Slivers	Not Supported
	Along-Line Label Character Spacing	Supported (Supported in version 12.0.0 and above)	MapBox handles labels along lines differently from SuperMap. Therefore, the display effect of labels along lines in vector tiles may differ from the original map, e.g., the effect of periodic spacing along lines. When a fixed text angle is set for labels along lines, the "Along-Line Label Drawing Type" must be set to "Entire Draw"; otherwise, the fixed text angle will be invalid in the vector tile.
	Along-Line Character Relative Angle	Not Supported
	Label Along-Line Mode	Not Supported
	Fixed Text Angle	Supported
	Remove Duplicate Labels	Not Supported
	Periodic Spacing Along Line	Supported
	Along-Line Label Drawing Type (Split Draw, Entire Draw, Compatible Draw, etc.)	Not Supported
Single-Value Label Thematic Map	Single-Value Field	Partially Supported	Only supports a single field; does not support field expressions or SQL function calculation results, e.g., name \|\| '_'\|\| type. For the same point dataset, if both a unique value thematic map and a single-value label thematic map based on that point dataset exist simultaneously, they must use the same field for their single-value fields.
Single-Value Label Thematic Map	Other Settings Content	Consistent with Uniform Label Thematic Map
Custom Thematic Map		Not Supported	If the map contains unsupported thematic maps, these thematic layers will be ignored during vector tile generation.
Matrix Label Thematic Map		Not Supported
Graduated Symbol Thematic Map		Not Supported
Statistical Thematic Map		Not Supported
Dot Density Thematic Map		Not Supported
Aggregation Maps (Heat Map, Grid Map, etc.)		Not Supported
4. Text Style
Font		Supported		Ensure the corresponding font file exists on the computer.
Text Color		Supported
Font Size		Supported
Font Effect	Bold	Supported	When text uses bold and italic effects, ensure the computer has the corresponding bold and italic font library files for that font, so that the bold and italic effects in the generated vector tiles are valid.
	Italic	Supported
	Outline	Supported
	Shadow	Not Supported
	Underline	Not Supported
	Strikethrough	Not Supported
	Rotation Angle	Supported
	Oblique (Left Oblique, Right Oblique, Oblique Angle)	Not Supported
	Fixed Size	Supported	During vector tile generation, text in the map needs to be set to fixed size; otherwise, the text display effect in the tiles may differ from the original map.
	Text Background	Not Supported	The text background will appear as a text outline in vector tiles.
	Superscript/Subscript	Not Supported
Text Layout	Multi-line text alignment, etc.	Not Supported
5. Point Symbols
System Point Symbols	System0	Not Supported	System0 square point symbols will appear as round point symbols in vector tiles. Workaround: Create a new point symbol by drawing a square geometry to make a square point symbol.
System Point Symbols	System1	Supported
Vector Point Symbols		Supported
Raster Point Symbols		Supported
Color		Supported
Symbol Rotation Angle		Supported
Symbol Transparency		Not Supported
Scale With Map		Not Supported
6. Line Symbols
System Line Types	System0, System1	Supported
System Line Types	System2, System3, System4	Not Supported	System2, System3, System4 line types will appear as solid lines in vector tiles. Alternative: Create a new line type, add a dash (system line type) sub-line, and adjust the sub-line's virtual-real mode to create the required dashed line type.
Custom Line Types		Supported	Custom line types support line symbols containing multiple sub-lines, but each sub-line's type must be "default".
Sub-Line Types	Dash (System Line Type)	Supported	Supports virtual-real mode.
Sub-Line Types	Other Sub-Line Types	Not Supported	Unsupported sub-lines will appear as solid lines in vector tiles.
Sub-Line Settings	End Symbol	Not Supported
Sub-Line Settings	Sub-Line Offset	Not Supported
Scale With Map		Not Supported
7. Fill Symbols
System Fill Symbols	System0, System1, System2, System3, System4, System5, System6, System7	Supported
Fill Symbol Outline		Consistent with Line Symbols	MapBox styles' support for area symbol outlines is consistent with that for line type symbols.
Custom Fill Symbols		Supported	Custom fill symbols only support symbols containing one fill sub-layer. The fill sub-layer can be an image filling or a symbol fill.
Fill Symbol Sub-Layers	Symbol Filling	Supported	Versions below 12.0.0: Support symbols containing only one sub-layer. Filling methods support point symbol filling, picture fill, pure filling, and linear filling. Version 12.0.0 and above: Support symbols containing multiple sub-layers. Filling methods support point symbol filling, picture fill, pure filling, and linear filling.
Fill Symbol Sub-Layers	Image Filling	Supported
Scale With Map		Not Supported
8. Map Properties Settings
Map Fixed Scales		Supported	Vector tiles are created using global scales. The fixed scales of the vector map need to be adjusted according to the global scales; otherwise, the visibility effect of map elements in the vector tiles may be inconsistent with the original map. The numerical values and precision of layer visible scales must exactly match the global scales.
Map Overlap Settings		Not Supported	Version 12.0.0 and above only supports the map overlap setting for turning off "Show/Hide Points with Text."
Fixed Symbol Angle		Not Supported
Fixed Text Angle		Not Supported
Fixed Text Direction		Not Supported
Line Antialiasing		Not Supported
Text Antialiasing		Not Supported
Label Weight Settings		Not Supported
9. Vector Tile Generation Configuration
Tile Scales	Global Scales	Supported
Tile Scales	Custom Scales	Not Supported
Tile Level Range	Continuous Scale Levels	Supported
Tile Level Range	Non-Continuous Scale Levels	Supported	If the scale levels are not continuous, the display effects at missing levels will be abnormal when viewing vector tiles.
Storage Format	Compact	Supported
	Original	Supported
	MongoDB	Supported
Storage Path	Local Directory	Supported
	Shared Directory	Not Supported
	FTP Directory	Not Supported
	Object Storage Path	Partially Supported	Only vector tiles in the original storage format can be stored in object storage.
Tile Bounds	Whole Map	Supported	Default tiling range.
	Current Window (Desktop)	Supported	Not supported by the GPA tool.
	Custom Bounds - Rectangle Range	Supported	Specified by "Left, Top, Right, Bottom" coordinate values in the GPA tool.
	Custom Bounds - Specify the Object (Desktop)	Supported	Not supported by the GPA tool.
	Custom Bounds - Custom Expression (Desktop)	Not Supported
Origin of Tile	Modify Origin of Tile	Not Supported
Vector Tile Parameters	Generate Font Cache File	Supported	Need to enable "Generate font cache file"; otherwise, the text content in the resulting vector tiles may be abnormal.
	Generate Vector Tiles	Supported	Generate vector tiles. In vector tile update scenarios