OCAD help Pt. 762

[Becks]

More OCAD help people! If I have an A3 photocopy of an aerial photo for a school that I want to turn into a nice friendly A4 map, then what's the best way to do it? Do I need to scan the image and whack it in or can i draw kinda freehand.

I really have no idea so basic advice on getting started would be much appreciated.

[Godders]

I'd recommend getting the photo scanned. You can then open it in OCAD as template (or 2 if you scan at A4) and draw the O map by tracing the photo.

[tokoloshe]

Play around with the brightness and contrast on the scanned image before drawing. You want something fairly bright. I find a greyish picture easier to work with than black and white high contrast

To get the parts aligned, if you are using an A4 scanner it may be better to do it in 3 parts so you have an overlap. That way you can ensure the scale and alignment is right - better still overlay on an OS map image - purely to align - and then close that template and draw from the photos.

[Safety]

Definetly scan it in and use as a template to draw over. I have the horrible suspision that OCAD still only accepts Bitmaps (.bmp) as templates (correct me if I'm wrong someone because I would like to know). This means the file size can be rater large. I have found for an A3 photo if you scan it as 2 A4 images. Trace over one, then line the second one up to your map. It greatly improves the speed of doing so because of the large .bmp file size.

If you are planning to draw it for A4 from A3, it is important you get the scales right. Work out what the scale of the photograph is not just the paper size. Set the template scale as what the map is and draw over it. You should then be able to re-scale it for printing out.

Hope that was helpful.

[Nails]

Dave you are being corrected...you can open bmp,gif,tiff or jpg in ocad, not to mention dxf and ai import.

Or have the arial and the os open at the same time and just select transparency.

Betterstill -use mapstudio for adobe illustrator.

[EriOL]

OCAD8 accepts gif, jpg and tiff but older versions of OCAD does only take bmp.

Getting the scale right is important, you need to know the scale and how many dpi the scan was made in when you open the template in OCAD. If you're working with an aerial photo you whould use the maximum resolution available. The built-in scanner-software in OCAD is kind of basic, but it works.

[SLOWGeek]

More OCAD help people! If I have an A3 photocopy of an aerial photo for a school that I want to turn into a nice friendly A4 map, then what's the best way to do it? Do I need to scan the image and whack it in or can i draw kinda freehand.

I really have no idea so basic advice on getting started would be much appreciated.

I don't know what sort of aerial photo you are refering to but... the stereo aerial photos you can buy from OS are taken from a plane with a camera pointing downwards however you cannot directly map this to a map since the position of the object in the photo is not just dependent on the location of the object but also it's height... e.g. tall objects tend to move in towards the center... the process to eliminate this distortion is 'orthorectification'; it's a good distortion to have because if you put two photos together you can derive height as well as location...

If your area is flat and the photo is from the top you should be OK but bear this in mind....

[Nails]

for christ sake shes talking about a school!

[Seamus]

when making maps for schools I often go to the local planning department and ask for their best map that fits on to A4. It should be free as long as you are using the map for the school. All local councils have a Service Level Agreement with OS that means they get all their area maps copyright free.

If they are going to charge you, make the school pay! Some councils have it in electronic form which means you can import direct into OCAD otherwise they scan it in for you are you open it up as a template.

I would use the arial map as a guide what i on the ground.

[SIman]

I see in the recent RC#5 that the BOF Map Group has produced guidelines and map specifications for use with OCAD for producing school maps. Looks worth reading - once you find it. (Here!)

[mharky]

so basically is ISSOM plus using your intelligence for special features...

[Nails]

Yep i don't know why bof bother with things like that -just making work when there isn't any -its not as if these symbol sets aren't available on the web already -and not as if you can't download them from ocad.com!

[redkite]

I am currently preparing a simple map of a local nature reserve with OCAD8 and am simply using the arial photo, bought from Getmapping or multimap as the template. Seems to be working ok. You just need to work out the scale. From memory think one pixel was 25cm on the ground.

[Ed]

what Getmapping/multimap sell as aerial photos aren't strictly speaking aerial photos - they're orthophotos that have been corrected for distortion due to the camera and the terrain relief and so can be used straightaway as the base for a map - if you tried that with a single raw aerial photo you'd end up with a very 'interesting' map...

[El]

Nails - I think the reason BOF bothered is so that all schools' maps are mapped to the same uniform standard. As I understand it up til now school mapping symbols have been a bit adhoc - guess this just standardises things.