1. Delete the outline decoration information.
The topographic map provided by surveying and mapping units is sometimes a regular topographic map with outline modification information, which is redundant for design and affects the release of design drawings and must be deleted.
2. Delete the redundant objects outside the map sheet.
In the process of topographic map making, sometimes some redundant objects are produced outside the map sheet, which are useless to the design, but will affect the design. Use AutoCAD ZOOM command to enlarge the topographic map to the maximum, and check whether there are redundant objects outside the map sheet. If there are redundant objects outside the map sheet, please delete them. Through the zoom command for many times, the useless objects outside the topographic map sheet are deleted.
3. Delete the redundant entities in the map.
In addition to the map sheet, there are redundant objects. For various reasons, there are more or less redundant objects in the topographic map sheet. Check the objects in the topographic map one by one, and confirm and delete the redundant objects in the topographic map, such as redundant lines, repeated administrative division notes, river name notes, etc.
4. Check whether the layer is closed or frozen.
Closed or frozen layers often appear in the delivered topographic map. Open the closed or frozen layers one by one for inspection. If it is not the necessary topographic map content, the cleaning should be deleted. If a topographic map is needed, the display should be turned on.
5. Delete duplicate entities
Some topographic maps have narrow scope and few elements, but many objects and large files. After checking, it is found that there are many duplicate objects. Although duplicate objects will not affect the publication, it will lead to the slow opening and display of topographic map files, which will have a great impact on the use. There are many reasons why topographic map objects are duplicated. For example, when drawing with CASS, there will be overlapping points, lines, blocks and text notes on the drawing due to operational reasons (such as copying, pasting or regenerating). If it is deleted manually, on the one hand, it is difficult to find out which overlapping entities are, on the other hand, it is a heavy workload. There are two ways to solve this problem:
① Use CASS software to "check warehousing → delete duplicate entities";
② Use AutoCAD command "Delete Duplicate Objects".
This helps to reduce the file size and improve the opening and display speed.
6, check the 0 layer
Set the current layer to layer 0, check whether there is an object on layer 0, and if there is, transfer it to the corresponding layer or create a new layer.
7. Clear the layer filter
In AutoCAD, the function of layer filtering is that when there are a large number of layers in the same drawing, they can be grouped according to their characteristics or characteristics, so as to filter out the layers with certain characteristics. Among them, the ways and means of filtering are: state filtering, layer name filtering, color filtering and linear filtering. Deleting the layer filter can reduce the file size.
8. Clear files
After the above processing, Purge is used to clean up the whole drawing, clear up useless information, reduce the file storage size, and improve the speed of file loading, processing and printing.
If the file is large, you can try to "write a block" with the Wblok command. Writing a block can clear a piece of useless content, such as a group, and sometimes it can effectively reduce the file size. At this time, if there is a user coordinate system in the topographic map, the user coordinate system will be lost after the block is written.
9. Convert 3D polyline into 2D polyline.
This is described in detail in "AutoCAD Crash when Using JSL- Route Expert System", and the extract is as follows:
10, the topographic map storage version is not recommended to use the low version.
This is also described in detail in AutoCAD crash when using route CAD software, and the extract is as follows:
By the way, I have made an in-depth study on the reduction of topographic map files, which are connected by several interconnected contour lines. According to my understanding of Dwg file, this process should be very effective. I wrote the function of "contour line connection". But in fact, several topographic maps have verified that the reduction of file size is very limited. For example, if the 50000+ contour line is reduced to 20000+ contour line, the number of entities will be reduced by more than half, and the file size will only be reduced by about 1MB, with the reduction ratio below 5%, and the actual effect is not obvious.
Topographic map is often used in survey and design, and it will get twice the result with half the effort if it is handled well; If it is not handled well, it will get twice the result with half the effort. For various problems in the process of topographic map processing, welcome to exchange and discuss.