If it needs to be a ramp to comply with regulations then there may already be something laid down governing it's design, manufacture & installation. A wheelchair ramp has a minimum 1 in 12 slope so there may be some figure covering this. Does it need to be wide enough for just the animal or a handler as well? Is there a minimum weight loading of any kind.
Once you have designed it is there anyone who you can run it by to make sure it is suitable before you go to the expense of manufacturing & installing it.