昨晚上QQ上一个朋友突然问,按说每年自杀上百万人,成功也有20来万,为什么单姜岩这事引起大家这么大的关注与愤慨?
仔细想了下,可能有这么几个原因
很多女性都有类似的被男人伤害的经历,所以她们感同身受,所以同情
男人们欣赏姜对爱情婚姻的执着专一,在这个物欲横流道德沦丧一切向金钱看的年代,更显得尤为可贵
其实从大家的反应看,对自杀行为大家还是理性看待的,大家欣赏的是执着和显示出来的才情,愤慨的是王家人的薄情
刚才看到北京有网友自发组织到王家抗议他们的行为
昨晚上QQ上一个朋友突然问,按说每年自杀上百万人,成功也有20来万,为什么单姜岩这事引起大家这么大的关注与愤慨?
仔细想了下,可能有这么几个原因
很多女性都有类似的被男人伤害的经历,所以她们感同身受,所以同情
男人们欣赏姜对爱情婚姻的执着专一,在这个物欲横流道德沦丧一切向金钱看的年代,更显得尤为可贵
其实从大家的反应看,对自杀行为大家还是理性看待的,大家欣赏的是执着和显示出来的才情,愤慨的是王家人的薄情
刚才看到北京有网友自发组织到王家抗议他们的行为
Zhuotong Nan (南卓铜) ([email protected])
ArcView 9.2 comes with some basic interpolation approaches, for example, inverse distance weighted, Kringing, etc. In some cases, we want interpolate based on areal weighted. For example, Radar measurement can produce rainfall data over a study area. In order to use those Radar rainfall in hydrological model, e.g., VIC model, with a 1/8 degree spatial resolution, we need to do interpolation from a higher resolution, e.g., 4km by 4km. As shown in Figure 1, each grey cell has a measured value from Radar. We would like to generate an appropriate value for a VIC cell which might cover several Radar cells. In this part, we will illustrate an areal weighted approach.
Figure 1 Radar rainfall cells and 1/8 deg VIC cells
ArcView 9.2 comes with a fishnet function (Data Management Tools → Feature Class → Create Fishnet) which is capable of generating a regular grid lines. However due to the limitation of ArcView license, it’s hard to implement conversion from polyline to polygon which is necessary to do areal weighted interpolation to be introduced in this section. Therefore, we will employ a free yet powerful script from ArcScripts website.
Figure 2 Customization dialog
Drag Create Fishnet to any place on toolbar. You will see on toolbar. Close Customize dialog.
Note, to uninstall the script, you can open Customize dialog again, and drag fishnet icon on toolbar to any place except toolbar.
VIC is a macroscale hydrologic model that solves full water and energy balances. It runs on basis of VIC grid. See http://ldas.gsfc.nasa.gov/LDAS8th/LDASspecs/LDASspecs.shtml for details of grid extent. We will generate VIC grid polygons using Fishnet utility download from ArcScripts in a scale of 1/8 degree.
Figure 3 Parameters for creating 1/8 degree VIC grid
Figure 4 Reproject to Albers Equal Area projection system
The produced vicgrd8_alb.shp now is in Albers Equal Area projection system. Note here we specified a transformation method to convert NAD_1927 to NAD_1983. Remember vicgrd8.shp is in NAD_1927 system and now vicgrd8_alb.shp is in NAD_1983 system.
xster=hrapx*4762.5 – 401*4762.5
yster=hrapy*4762.5-1601*4762.5
Copy 0703200407z.asc to 0703200407z_ster.asc. Then open 0703200407z_ster.asc using any text editor, change its header to,
ncols 335
nrows 159
xllcorner -161925
yllcorner -6372225
cellsize 4762.5
Save 0703200407z_ster.asc.
ASCIIToRaster c:workspacelab2703200407z_ster.asc c:workspacelab2g0703200407z FLOAT
In ArcCatalog, right click g0703200407z to open its Properties window. Navigate to Spatial Reference section, click Edit… to define its spatial reference. Choose Define the coordinate system interactively. Select Stereographic (Polar view) and configure it as shown below.
Figure 5 Parameters for Polar Ster projection system
The conversion from raster to polygon only support grid file in integer. To do this, run following commands in Command Line Window.
Times_sa c:workspacelab2g0703200407z 100 c:workspacelab2g07032004_100
Int_sa c:workspacelab2g07032004_100 c:workspacelab2g07032004int
At this point, the produced g07032004int is already an integer grid file.
RasterToPolygon c:workspacelab2g07032004int c:workspacelab2g0703200407_poly NO_SIMPLIFY VALUE
A field “GRIDCODE” in the generated polygon (g0703200407_poly) is corresponding to cell values in g07032004int, which is 100 times real rainfall value.
Using Data Management Tools → Projections and Transformations → Feature → Project in ArcToolbox to project g0703200407_poly in Polar Stereographic coordinate system to g0703200407_alb in Albers Equal Area Coordinate System. This target coordinate system can be imported from vicgrd8_alb.shp.
Using CalculateAreas command to calculate area for each VIC cell in Command Line Window.
CalculateAreas c:workspacelab2vicgrd8_alb.shp c:workspacelab2vicgrd8_alb_area.shp
The field “F_AREA” in vicgrd8_alb_area.shp indicates area in square meter.
Intersect utility is used to calculate areal contribution from XMRG polygons to each VIC cell.
Workspace c:workspacelab2
Clip_analysis vicgrd8_alb_area g0703200407_alb c:workspacelab2vicgrd8_clp.shp
Figure 6 Intersect input parameters
Figure 7 Attribute table of intersect.shp
Here FID_vicgrd and F_AREA come from VIC cells, while FID_g07032 and GRIDCODE come from XMRG polygon file. FID_vicgrd uniquely represents each VIC cell whose area is show in F_AREA field. GRIDCODE is actually equal to 100 * rainfall.
Querying attribute, for example FID_vicgrd = 1400, will extract all small polygons consisting a VIC cell.
Open intersect.shp’s attribute table, Click Options → Add Field…
Figure 8 Add a new field
Click the header of VIC_AREA column to select this field, right click it then select Field Calculator…, Yes upon warning message. Input [F_AREA] in the lower textbox then click OK to start calculation.
Figure 9 Field calculator
CalculateAreas intersect c:workspacelab2inters_area
Figure 10 Calculate Percentage field
Make inters_area layer visible, and make sure there is no selection in this layer. Otherwise use on the Tools toolbar to clear any existing selection. In ArcToolbox, run Analysis Tools → Statistics → Summary Statistics to calculate rainfalls cell by cell.
Figure 11 Summary statistics
Figure 12 Join to rainfalls.dbf
Figure 13 Make field name self-explanatory
In order to use in combination with other raster, we can also convert this polygon shapefile to raster using FeatureToRaster command in Command Line Window.
Figure 20 Symbology
Figure 21 Exported map
Although ArcView 9.2 has already included some basic interpolation approaches, it turns out in many cases hard to meet our specific requirements. This handout walks through how to interpolate Radar rainfall data to 1/8 degree VIC grid, illustrating necessary steps to implement areal weighted interpolation approach using ArcView. This handout also show us essential GIS operations such as project, clip, intersect, export, manipulate attribute table, link feature class to external table, etc, as well as making use of third party script.
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