I have been involved in a project requiring a significant amount of GIS editing. As part of this process I have evaluated the most reliable and efficient tools for polygon editing. My basic requirements were:

• snapping to vertices during add/split
• Easy to move around/zoom in/out/pan while editing
• reliable

Fortunately, I was able to assess the process across most GIS packages, and this how they fared:

MapInfo - Editing is quite laborious, involving several steps for simple tasks. Autocompleting a polygon (i.e. adding to existing geometry) required me to trace over the existing geometry - not ideal. There is also no facility to edit attributes directly after edit (except for the "i" tool)

ArcView 3.1 - No reliable snapping during polygon edit (i.e split or autocomplete polygon). There is no facility to edit attributes directly after edit.

ArcMap - All tools function perfectly, and snapping is intuitive. The only problem with this is that it crashed three times and I lost my data three times (essentially a day's work). I could not reliably carry on with the fear of data loss on my shoulder

GeoMedia - All the signs for it doing the job efficiently, except the polygon autocomplete was extremely difficult to use and did not operate the same all the time. Also required that I trace over existing boundaries to complete my polygon. Not ideal.

I have been seriously considering Manifold for the past 12 months, as I have often been trying to do a complex operation, and time after time have read that "Manifold does that out of the box". Add to this all the hype that has been going around, I did a quick bit of research about its editing capabilities, and, after getting favourable responses, we took the plunge and bought it! Now it was time to try it out.

First off, I must admit that my GIS career has primarily been based upon ESRI software. That is, while learning the fundamentals of GIS, I had ArcINFO, then ArcView as my companion. That was first approximately 15 years ago. The way I approach things is therefore definitely biased towards the ESRI way, and I have considered this. That said, fundamentals are fundamentals, and I beleive that any experienced GIS user should be able to pick up a package and find their way around in a relatively short space of time. I have also had the fortune of working for extended periods of time in both Mapinfo and GeoMedia. In both cases, these were easy to pick up and I was flying in no time.

So lets fire up Manifold...

The first thing, that all users say is that you must spend a bit of time getting to understand the manifold engine room. I followed these instructions and spent a solid 4 hours reading, researching and doing. From the onset, I was able to easily navigate and find my way around. In no time at all I had imported a shapefile and a tab file. With the help file at hand, I had my map styled how I wanted it, and was ready to start my task at hand. Just as a quick summary, the base GIS data is called a "drawing" (Mapinfo calls it a "table" and arcview calls it a "layer"). After importing, we can create a "map" window with the appropriate layers, and this is how manifold stores its data, in the "map" file. More about that later. From the project window, we can access the database behind the vectors, and this is all familiar windows like operations. Changing layer styles and creating thematic maps is relatively simple but not entirely intrinsic. The big test was to be related to my task at hand, and that is editing vector data.

At this point I should add that it is documented (via the Internet) that Manifolds greatest strength is in its data processing, and this assessment does not take this into account as I have not tried it. I have also not really tried creating a print or layout, except for a momentary fiddle. It did not appear to be entirely simple, and I think it would battle to compete with the ArcMap cartographic abilities, which I still believe are ahead of the pack. But GIS is not about making it maps, it is about taking data and producing answers - so let's forget about that for now.

Right, so lets go back to my task. I need to be able to:

• split polygons (these are called "areas" in manifold)
• Create polygons
• Autocomplete polygons (i.e. attach new polygons to existing ones)
• Select single/multiple polygons
• Easily edit attribute data
• Easily snap to edges and vertices

and do all this without the application crashing and me loosing all my data!

Selecting

A critical component of GIS. There are essentially three types of selections; interactive selection, tabular selection and spatial selection. Manifold wins hands down on its spatial and tabular selection. Easy to use SQL based queries produces fast accurate selection sets. A real pain however is their interactive selection tools. The selection tools amount to a total of 19 individual tools and three separate toolbars.

• The first toolbar controls how we are selecting (point, shape, freeform, box, box on centre, circle, circle on centre, ellipse, ellipse on centre).
• The second toolbar allows us to choose what we are selecting (lines, areas, points, pixels)
• The third toolbar allows us to define how we are selecting (new, add to, subtract from, inverse, intersection)

I have been involved in a project requiring a significant amount of GIS editing. As part of this process I have evaluated the most reliable and efficient tools for polygon editing. My basic requirements were:

• snapping to vertices during add/split
• Easy to move around/zoom in/out/pan while editing
• reliable

Fortunately, I was able to assess the process across most GIS packages, and this how they fared:

MapInfo - Editing is quite laborious, involving several steps for simple tasks. Autocompleting a polygon (i.e. adding to existing geometry) required me to trace over the existing geometry - not ideal. There is also no facility to edit attributes directly after edit (except for the "i" tool)

ArcView 3.1 - No reliable snapping during polygon edit (i.e split or autocomplete polygon). There is no facility to edit attributes directly after edit.

ArcMap - All tools function perfectly, and snapping is intuitive. The only problem with this is that it crashed three times and I lost my data three times (essentially a day's work). I could not reliably carry on with the fear of data loss on my shoulder

GeoMedia - All the signs for it doing the job efficiently, except the polygon autocomplete was extremely difficult to use and did not operate the same all the time. Also required that I trace over existing boundaries to complete my polygon. Not ideal.

I have been seriously considering Manifold for the past 12 months, as I have often been trying to do a complex operation, and time after time have read that "Manifold does that out of the box". Add to this all the hype that has been going around, I did a quick bit of research about its editing capabilities, and, after getting favourable responses, we took the plunge and bought it! Now it was time to try it out.

First off, I must admit that my GIS career has primarily been based upon ESRI software. That is, while learning the fundamentals of GIS, I had ArcINFO, then ArcView as my companion. That was first approximately 15 years ago. The way I approach things is therefore definitely biased towards the ESRI way, and I have considered this. That said, fundamentals are fundamentals, and I beleive that any experienced GIS user should be able to pick up a package and find their way around in a relatively short space of time. I have also had the fortune of working for extended periods of time in both Mapinfo and GeoMedia. In both cases, these were easy to pick up and I was flying in no time.

So lets fire up Manifold...

The first thing, that all users say is that you must spend a bit of time getting to understand the manifold engine room. I followed these instructions and spent a solid 4 hours reading, researching and doing. From the onset, I was able to easily navigate and find my way around. In no time at all I had imported a shapefile and a tab file. With the help file at hand, I had my map styled how I wanted it, and was ready to start my task at hand. Just as a quick summary, the base GIS data is called a "drawing" (Mapinfo calls it a "table" and arcview calls it a "layer"). After importing, we can create a "map" window with the appropriate layers, and this is how manifold stores its data, in the "map" file. More about that later. From the project window, we can access the database behind the vectors, and this is all familiar windows like operations. Changing layer styles and creating thematic maps is relatively simple but not entirely intrinsic. The big test was to be related to my task at hand, and that is editing vector data.

At this point I should add that it is documented (via the Internet) that Manifolds greatest strength is in its data processing, and this assessment does not take this into account as I have not tried it. I have also not really tried creating a print or layout, except for a momentary fiddle. It did not appear to be entirely simple, and I think it would battle to compete with the ArcMap cartographic abilities, which I still believe are ahead of the pack. But GIS is not about making it maps, it is about taking data and producing answers - so let's forget about that for now.

Right, so lets go back to my task. I need to be able to:

• split polygons (these are called "areas" in manifold)
• Create polygons
• Autocomplete polygons (i.e. attach new polygons to existing ones)
• Select single/multiple polygons
• Easily edit attribute data
• Easily snap to edges and vertices

and do all this without the application crashing and me loosing all my data!

Selecting

A critical component of GIS. There are essentially three types of selections; interactive selection, tabular selection and spatial selection. Manifold wins hands down on its spatial and tabular selection. Easy to use SQL based queries produces fast accurate selection sets. A real pain however is their interactive selection tools. The selection tools amount to a total of 19 individual tools and three separate toolbars.

• The first toolbar controls how we are selecting (point, shape, freeform, box, box on centre, circle, circle on centre, ellipse, ellipse on centre).
• The second toolbar allows us to choose what we are selecting (lines, areas, points, pixels)
• The third toolbar allows us to define how we are selecting (new, add to, subtract from, inverse, intersection)

In my opinion, the first toolbar is overkill. A box select can act as a point select or a box select in one. Then all you need is the polygon select. The circle and the ellipse select seem like a good idea, but I can honestly say in my years in GIS, I have rarely needed them. The same goes for the "on centre" tools and the freeform - nice idea, but not critical.

The select toolbar is necessary because a manifold drawing can consist of points, lines or areas, and therefore makes specific selection much easier. That said, I never utilised the advantage of multiple geometries in Mapinfo, so I doubt I will do it here (must be my ESRI background ).

The third toolbar baffles me, and I will explain why. I have previously read a long dissertation by the "infamous" Dimitri about how much Manifold is in line with Microsoft technologies and user interfaces, more so than any other GIS package. If this is the case, why then do I need� separate tools to add to a selection, subtract from a selection, and restart a selection, when I could simply have one tool and make use of the "Shift" and Ctrl" key. If something is already selected, Ctrl-click will deselect it, and if it is not selected, it will select it..simple! In addition to this I found that with the "add to selection" tool, sometimes I can ctrl-click and sometimes I cannot (perhaps a bug). Also, I cannot seem to find any way of customising my toolbars (a fundamental Microsoft/Windows practice), that way I could get rid of all those circle and ellipse selects that I will not use, and take some clutter off my toolbar.

All in all, spatial and tabular selecting works fantastic, interactive selecting works, but could defiantly be improved upon.

Splitting polygons

Splitting works much the same way in Manifold as it does in Mapinfo. You essentially have a dummy drawing/layer (or you can use the same drawing) and draw a line across the polygon where you would like to split. Select the polygon and then use a handy little toolbar at the bottom of your screen (transform toolbar) and split the polygon. you can then select the line and delete it. Here is an example of the transform toolbar doing such an operation (I might add here, that this handy little toolbar provides quick access to a myriad of other spatial tools, as shown below)

All in all, splitting is easy, and relatively painless, but I still find ESRI's split tool slightly easier to use.

Autocompleting polygons

This is one area, where I truly believe Manifold could improve on. ESRI's autocomplete tool is easy and efficient. Consider the following situation:

In ArcMap/Arcview you would fill in the "hole" using the autocomplete tool by doing the following:

• - Start a line inside the polygon to the left of A
• - Snap to the corner point at A using "snap tools"
• - Snap to point H
• - draw the line anywhere to the right of F and G
• - snap to E
• - snap to D
• - Double click inside the polygon to the left of D to complete.

This will create a topologically correct polygon in that place

In Manifold, you would choose the "Insert Area" tool and then do the following

• - Snap to point A
• - Snap to Point B
• - Snap to as many vertices as there are between B and D (i.e. C). In this example there are at least 9
• - Snap to D
• - Snap to E
• - Snap to F
• - Snap to G
• - Snap to H
• - Right click to finish

Although their snapping tools are very good, and you can control what layers can be snapped to, and wether you should snap to areas, points or lines, or all three; you are still bound to end up with slithers in a more complex example. Please do however note, that I am still assessing if there is an easier way to do this, but cannot see any at this stage.

Alternatively, you could also draw the area in another layer and "automatically trace" (called autocomplete in manifold, but I do not want to confuse the issue) the existing lines, and then Ctrl-C copy the area, and Ctrl-V paste it into the correct layer. This essentially draws the line for you. This is relatively simple, but does not seem to work in a situation such as this example, because it has an open end. It only seems to work in the situation of a "hole".

All in All, ESRI's autocomplete tool is still the best tool for this task

Creating Areas

Creating areas is basic, and operates the same across all GIS packages. An advantage that Manifold has is its tool for automatic tracing. Generally when you are adding polygons, you are tracing existing features. Manifold makes this a breeze by doing the bulk of it automatically (and apparently, has image tracing support, which I have not investigated). Manifold does this task efficiently and effectively.

Snapping

As I have said, Manifold has excellent snapping facilties, and I I have been adequately impressed with them

Editing Attribute Data

With Manifold, you can optionally force it to pop up an attribute Edit window immediately after any polygon edit. This makes editing relatively painless. Other GIS packages do have such a facility, so it is not a deal breaker, but the advantage is that it happens automatically (Geomedia also does this). Both Mapinfo and ArcMap require the user to select the edit window. Anotehr nice feature I stumbled upon is related to the table. If the user selects a series of polygons of the same attribute type, and then opens the table, and filters to only show the selection (one button click); you can edit one of the records and it will automatically assign the same value to all the other records.

The only recommendation I could make with regard to the Automatic edit popup, is the ability to associate lookup tables with individual fields, there reducing the possibility of finger error.

And the most important feature is.....

All in all (I don't think because I am of ESRI origin), I think the splitting and autocompleting tools of ESRI are better, and more intuitive, however, I will not use them in fear of the program crashing and me losing all my data. Manifold is....so far anyway.... stable, I have has it running now for four days, and set my laptop into standby mode multiple times and it is still operating fine. At the moment, that is the more important than anything else. If we have no confidence in our GIS to look after our data, then we may as well give it up.

Other comments

Part two will see my assessment of the anlysis tools (this is what I am looking forward to) and the scripting, and my viewpoint of the data storage format of manifold (the map file). I am not convinced about the map file format, but cannot comment until I have used it more. In summary, It is not that difficult to get to grips with. Not nearly as much as everyone says. I would say a Mapinfo user would adjust easier than an Esrilite.

A final comment, not related to usability of the product at all. I wish the Manifold user base would move away from this abrasive and negative attitude towards ESRI. There seems to be a trend of always trying to promote Manifold, by saying how rubbish ESRI products are. ArcMap and ArcGIS are good products. Yes, you have to pay through your nose to get all the functionality you want, and yes, it is unstable. This will come to fruition in due course - wether it be through increased sales or decreased sales. By all means tell the world what Manifold can do, and teel them how cheap it is, but try and not do it through a process of knocking ESRI. Mapinfo is also comparatively expensive, as is GeoMedia