At ArcGIS 10, ESRI is trying to further tie the ArcGIS brand with online integration. So they are launching ArcGIS.com, which from what I can gather is a fusion of ArcGIS Online and the ArcGIS Resource Centers. It is also intended to expand their efforts to make a community focused site, allowing more flexible sharing of maps and apps, and making it easier to discover both. I'm getting a little bit of a Microsoft Bing vibe from it.

Another exciting development is creating an online version of ArcGIS Explorer, named (you-guessed-it) ArcGIS Explorer Online. It is based on Silverlight and does many of the same things that the desktop version does, such as measuring, markups and the presentation mode. All that is required is to have the Silverlight API, otherwise no other components need to be installed. I was very impressed by the demo shown at the 2010 Dev Summit (http://www.esri.com/events/devsummit/videos/video3.html). I am curious to know if it will be a free deployable app like the Flex viewer or the desktop ArcGIS Explorer.

A new feature at ArcGIS 10 is the ability to create a map package (file extension of MPK) using all the data that is in a map document (MXD). It will act just like the layer package that was introduced at ArcGIS 9.3.1. The package includes the map document (version 10 mxd) and the data (even if the data is from diverse places).

The map package will self extract using the ArcGIS File Handler utility (ArcGISFilehandler.exe utility in your Program Files\Common Files\ArcGIS\bin folder, it also automatically installed with ArcGIS Explorer 900), it will by default place the files in your My Documents (XP) / Documents (Vista & Win7) > ArcGIS > Packages.

This is a great way to share a whole map with someone at a different location, however they will need to have ArcGIS 10, it won't work in ArcGIS 9.x. You will also be able to upload map packages to ArcGIS Online.

Note: I'm part of the ArcGIS 9.4/10 beta, and that is how I found out about that information.

Projections and transformations can be very confusing, especially if you don't do it very often. A common transformation when working with North American datasets is NAD 83 projections to WGS 84 (Latitude & Longitude). When you use the Project tool found in ArcToolbox > Data Management Tools > Projections and Transformations > Feature (or Raster) > Project, you need to specify which Geographic Transformation you need to use. Below is a guide :

First part is the name of the transformation -> Second part is the code -> Third part is the area of use (where is the data located that is being transformed).

• NAD_1983_To_WGS_1984_1 -> 1188 -> Canada, Central America, Mexico, and United States (Alaska, CONUS)
• NAD_1983_To_WGS_1984_2 -> 1251 -> United States - Alaska - Aleutians
• NAD_1983_To_WGS_1984_3 -> 1252 -> United States - Hawai'i
• NAD_1983_To_WGS_1984_4 -> 1308 -> United States - CORS ITRF94
• NAD_1983_To_WGS_1984_5 -> 1515 -> United States - CORS ITRF96
• NAD_1983_To_WGS_1984_6 -> 1696 -> Canada - Quebec
• NAD_1983_To_WGS_1984_7 -> 1697 -> Canada – Saskatchewan
• NAD_1983_To_WGS_1984_8 -> 1702 -> Canada – Alberta

The above was taken directly from a document installed with ArcGIS, it's usually found at C:\Program Files\ArcGIS\Documentation\geographic_transformations.pdf.