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人生第一个Offer

其实拿到Offer很久了,没时间写,就记下吧,2008年12月24日。
分类:Live | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 567

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Importing a USGS DEM for Use in ArcGIS

About DEMs

A DEM is a digital elevation model. It can be used in ArcView's Spatial Analyst, Model Builder, and 3-D Analyst extensions. To read up more about DEMs, go to the USGS National Spatial Data Clearinghouse DEM web site.

DEM Sources for Texas
TNRIS serves the 1996 Digital Elevation Models at 30 meter pixel resolution - see the TNRIS Digital Data-DEMs site for more information.  DEMs at TNRIS are identified by their USGS Quad Map name - see the USGS Quad and Quarterquad Locator Map to know which DEM you will need. DEM data from TNRIS is in USGS DEM format.

Unzip the file (it will have a name like 3097420g.zip) and you should see a new set of files. The file that ends in .dem is the actual digital elevation model in USGS format (e.g., 3097420g.dem)

Important information! The TNRIS DEMs are usually in the UTM coordinate system, NAD 27, Zone 14 for most of central Texas, and map units (x,y horizontal units) are meters. Some of the elevation data in these DEMs is in meters and some is in feet. It is very important that you know which! Once you bring up the data, examine it in ArcMap to determine this if possible.

Other DEM sources
DEM data is available from the Federal government in SDTS format, and from many state agencies.

Importing a USGS format DEM in ArcGIS
Note: The following instructions will only work if you DEM is in USGS format. Most DEMs from the USGS are not in USGS format (go figure...) - it is in SDTS format (but the USGS is also now producing DEMs in other formats including ArcGrid). If  your DEM is in SDTS format (Spatial Data Transfer Standard), you will need to use the Import SDTS Raster to Grid tool in ArcToolbox.

After you download the DEM, you need to unzip it. Once it is unzipped, you can import it into ArcGIS.

  • Start ArcToolbox, and choose Conversion Tools - Import to Raster - DEM to Grid. Read the Help information before you begin, then follow the instructions.

  • The USGS DEM is the file that ends in .dem (e.g., 3097420g.dem)

  • Leave all the defaults as they are for now - we will talk about these in class.

  • For output grid, you can navigate to your personal folder and type in a new name - this will be the final ESRI formatted DEM that you will work with, so give it a good name, like the name of the quad map it represents (e.g., austin_west). But read this carefully - you cannot specify a folder that has spaces in the folder name; in fact, no folder in the entire path on the computer can have spaces in it (don't ask me why). So the folder path to this new grid needs to be something like C:\temp\edwards_group\dem\austin_west

  • Once the importing process is done, take a look at the results in file manager or explorer - notice that there are now two folders, one called the name that you gave the grid (e.g., austin_west) and one called info. This is an ArcInfo formatted GIS data set.

  • Next add the new grid to a data frame in ArcMap.

Using a DEM in ArcGIS

  • To use a DEM in ArcGIS, you need the Spatial Analyst extension. In ArcMap, go to Tools - Extensions and make sure that Spatial Analyst is checkmarked.

  • Next, choose View - Toolbars and turn on the Spatial Analyst toolbar.

  • To create a hillshade map once your DEM is in view, click on the Spatial Analyst toolbar and choose Surface Analysis - Hillshade. Accept the default settings first, then try again and play around with the settings. Be default, this will create a temporary file. If you want to create a permanent file, click on the Output Raster section, navigate to your personal folder , and give the hillshade file a new name.

  • To create a slope map, you can use the Surface Analysis - Slope command. Beware, your horizontal map units must be the same unit as your elevation units (e.g., both feet or both meters) - often they are in different units, in which case you need to do some additional preparation! See Working with x, y, and z units in Digital Elevation Models for details and instructions.

  • If you need to re-project the grid to a different coordinate system, ArcToolbox has projection tools for grids under the Data Management area. The define projection wizard for grids is different than for shape files, and a little trickier. The necessary parameters are: the projection is UTM, zone 14, meters, no x,y shift, and the datum is NAD 1927 US Nadcon

  • For more information about Spatial Analyst, go to ArcGIS Desktop Help or the digital manual, Using ArcGIS Spatial Analyst.

Tags: GIS

分类:GIS | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 1107

12

03

Ubuntu Linux系统下Apt-get命令参数详解

常用的APT命令参数:

apt-cache search package 搜索包
apt-cache show package 获取包的相关信息,如说明、大小、版本等
sudo apt-get install package 安装包

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分类:System | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 811

12

02

在linux下发的第一篇日志

终于能在linux下发帖了,感觉耳目一新!linux是个好东西 !
分类:System | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 612

11

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SQL字符处理大全

select语句中只能使用sql函数对字段进行操作(链接sql server),

select 字段1 from 表1 where 字段1.IndexOf("云")=1;

这条语句不对的原因是indexof()函数不是sql函数,改成sql对应的函数就可以了。

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Tags: Code

分类:Database | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 519

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关于Chr(0)

刚才把Chr(10)错误写成了Chr(0),结果,Chr(0)以后的东西都显示不出来,真的狂汗,Chr(0)那么厉害,还以为哪里错了!
引用内容 引用内容
chr(0)到chr(31)是非显示字符,有特殊含义。  
chr(32)是空格,   chr(7)   表示beep   chr(0)是null。

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Tags: Code

分类:Coding | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 564
今天编项目的时候出现了一个“编译错误:只有定义在公共模块中用户定义类型能和变体类型相互转换或传递给后期绑定功能 ”,看了很久都看不明白这个奇异的错误,后来居然发现了一个傻人才犯的错误!把类名当结构用来作返回值了!当然是不小心写漏了几个字母!汗!

Tags: Code

分类:Coding | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 762

11

12

vb 读写配置文件(.ini)

可以使用两个API实现配置文件的读写
读:GetPrivateProfileString
写:WritePrivateProfileString

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Tags: Code

分类:Coding | 固定链接 | 评论: 0 | 引用: 0 | 查看次数: 1112
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