ArcGIS Pro creates a space-time cube by converging points

Space-time cube

By aggregating a set of points into space-time bins, they are summarized into the netCDF data structure. Calculate points within each bar and aggregate the specified attributes. For all bar positions, evaluate the counting trend and summary field values.

NetCDF (Network Common Data Format) is a file format used to store multidimensional scientific data (variables) such as temperature, humidity, air pressure, wind speed and wind direction. In ArcGIS, by creating a layer or table view based on a NetCDF file, one dimension (such as time) can be used to display all the above variables.

Examples of netCDF data: Left—Temperature; Right—Pressure at specific locations

principle

• The Create Space-Time Cube by Aggregating Points tool can aggregate the point input features into space-time bins. The created data structure can be regarded as a three-dimensional cube composed of time-space bars, where x and y dimensions represent space, and t dimension represents time.

• Each bar has a fixed position in space (x, y) and time (t). The bars covering the same (x, y) area share the same location ID. Bars containing the same duration share the same time step ID. Even if the point data is not rectangular, the cube is always rectangular, so some locations will have zero point counts in all time steps. For many analyses, only locations with data (at least one point count for at least one time step is greater than 1) will be included in the analysis.
  
• Each bar in the space-time cube has LOCATION_ID, time_step_ID, COUNT values ​​and the values ​​of all summary fields aggregated after the cube is created. Bars related to the same physical location will share the same location ID, and the combination of these bars can represent a time series. Bars related to the same time step interval will share the same time step ID, and these bars can be combined to form a time slice. The count value of each bar reflects the number of points that appear at the relevant position within the relevant time step interval.
• For detailed official documents, please refer to Creating Space-Time Cubes by Aggregating Points

Example

Data download

Let's take the national monthly precipitation as an example:

• First, you can download the hydrological data of the Chinese station through the US NOAA website, click https://gis.ncdc.noaa.gov/maps/ , select the time-related map, and select the appropriate time. This example uses monthly data.
• Check the global monthly summary data, click the wrench in the red box, the selection tool will pop up, select the country based on the location, and click Zoom to location
  
• At this time, the outline of the range will appear. Click Results to select all the data.

• Select CSV format data

• Select the data time and click CONTINUE.
  
• Select the data according to your needs (this example needs to select Precipitation precipitation data, and the temperature data is Fahrenheit, which can be converted to Celsius according to (Fahrenheit-32)×5÷9), click CONTINUE.

• Fill in the valid email address that you have received, click SUBMIT ORDER to submit the order, and you will receive the order email and data email in the mailbox later.
• Just click download in the data mail.
• The data result is shown in the figure (note that DATE is converted to yyyy-mm-dd format):
  

Create project and projection

• First open ArcGIS Pro and create a partial scene project.
  
• Select "China Map Gray Version" in the map—>base map
  
  
• Map—>Add Data—>Add XY point data, in the pop-up geoprocessing menu, select the precipitation table, the X field corresponds to the longitude, the Y field corresponds to the latitude, the coordinate system is WGS84 geographic coordinates, click to run.
  
  
  
• The space-time cube needs a projected coordinate system, so we change the projection of the data and scene. Right-click the scene graph frame in the content list, click Properties, select Coordinate System, and change the current XY to WGS 1984 World Mercator.
  
  
• Analysis—>Tools—>Toolbox—>Data Management Tools—>Projection and Transformation—>Projection, select the XY point data, and the output coordinates can be selected to be consistent with the scene, or you can choose WGS 1984 World Mercator by yourself and click to run.
  

Create space-time cube

• Create Space-Time Cube Tool by Aggregating Points In Toolbox -> Space-Time Mode Mining Tool, you can also search for Space-Time Cube tool directly.

• Select the point element file after projection, select the position of the output space-time cube, and select the time field. Since this data statistics are monthly precipitation, the time step interval is entered as 1, and the unit is month (note that the data must meet at least 10 steps Interval can be executed). Time step alignment is the default, because the data itself is spaced by 1, so there is no special need for alignment. The aggregation shape and the distance interval represent the size of the space and time bars, and can be defaulted if there is no special need. The summary field is used to count the sum/mean/maximum/minimum value of the field in the unit cube. Just use zeros to fill empty cube tiles. For a detailed description of this part, you can refer to the official document and working principle
  
• Generate a message report, where the error record is that the original data is empty and filled with zeros. Temporal outliers are mainly true records of the month.
  
• Open the space-time cube in 3D mode.
  
  
• Since the classification of symbols has not been changed, there may be some extremely low value marks that will be white, and the classification strategy can be adjusted in the symbol system.

• You can then use the time slider to browse the 3D results. Right-click the layer property and select time.
  
• Set the span to 0, uncheck the use time span, and set the step interval to 1 month.

Click the time button on the left side of the time slider to enable time, then use the arrows or the play button to browse the results in the space-time cube.

• The effect is as follows:
  

• You can also lock the start time to form a bar display.
  

• The effect is as follows:

Emerging time and space analysis

Emerging hot spot analysis tools can identify trends in data. For example, it can find new, enhanced, reduced, and scattered hot and cold spots. How Hot Spot Analysis (Getis-Ord Gi*) works

• After execution, use the 3D mode to display the original space-time cube again. At this time, there are more hot and cold spots in the theme.
  
• Get the analysis result
  
  This sharing roughly introduces the basic operation steps of the space-time cube. The specific principles and actual use need to be carefully studied in accordance with the official documents.