Here lately there has been some confusion as to when to use Orion's Network Atlas for topology mapping and network diagramming vs. using LANsurveyor so I thought I'd take this opportunity to share my thoughts on the subject.
There are two primary use cases for applications that do network/topology mapping and I think the easiest way to explain when to use each of these two products is by analyzing these use cases.
Network Monitoring - if you're looking to create network diagrams and/or topology maps for the purposes of enhancing your network monitoring dashboards - use Network Atlas. As a matter of fact, if you're planning to use the maps in Orion in any way just go straight to Network Atlas. It'll save you a lot of time and the latest version offers features around automatically adding topology, connecting devices, and adding new devices that make it a no-brainer if you're planning to use the maps as a part of your monitoring strategy.
Documentation If you're looking for a light-weight utility to run on your laptop to help you discover and map out the network then LANsurveyor is the ticket. The maps that you create and maintain for this use case are intended for documentation, asset tracking, light inventory management, and etc. LANsurveyor maps all the way down to the desktop and/or printer whereas Network Atlas is focused at the infrastructure level. LANsurveyor also allows you to export the topology maps into Microsoft Visio which makes for easy editing and printing. Also, if you're a consultant and you constantly go visit clients and need to get a quick understanding of their network topology LANsurveyor does a great job of this.
If you own Orion and you need to maintain detailed diagrams of network topology and device connectivity, I still say go with Network Atlas. When you buy Orion you are able to run as many copies of Network Atlas as you want to so that you can install it on your desktop and create the maps from there. Many folks that use Orion create maps that serve both purposes - monitoring dashboards and network documentation. If you can combine those efforts you can save a lot of time, especially if your focus is at the infrastructure level vs. all the way down to the end user devices on the LAN. The catch is that if you use Network Atlas then you'll need to use the maps within Orion and Network Atlas. It doesn't offer the option of exporting to Visio like LANsurveyor does.
When to buy both... If you're an Orion customer then you've got access to Network Atlas to create and maintain your network topology maps. However, in some cases you may also want to have a few copies of LANsurveyor to do documentation, take with you when you visit remote offices and need to get a quick snapshot of the network, or just to help map out and keep track of the devices on your LANs like PCs and printers. Especially if you're addicted to keeping your maps in Visio.
Hopefully this will help to clear things up a bit. Ping me back if you have comments or questions, but at the end of the day, as long as you're mapping out your network topology and keeping network diagrams of your infrastructure you're ahead of the pack - so get started...