I'm not sure that I would consider a half mile hike a trek! but typically the grading of a hike or climb deals with how strenuous they are, and the amount of time required to accomplish these hikes.
You've given us a 1/2 mile hike that had an altitude gain of 450 feet. I usually consider an elevation gain of 1000 ft in one mile that is continuous to be a strenuous hike and depending on where the hike took place (was it exposed (near the edge of a cliff where a fall on the trail could be fatal)) It's grade of difficulty is subjective, your hike was very short to really have a large degree of difficulty.
Hiking is also graded by the YDS (Yosemite Decimal system) and your altitude gain would be as a 3 or 4. Because the hike you took was only a half mile, it could be accomplished in a short time so it would be a 4 with a class roman numeral I, degree of difficulty. An extremely difficult hike would be a 4 with an III or IV degree of difficulty.
YDS Class
The system consists of five classes indicating the technical difficulty of the hardest section:
Class 1 is walking with a low chance of injury and a fall unlikely to be fatal.
Classes 2 and 3 are steeper scrambling with increased exposure and a greater chance of severe injury, but falls are not always fatal.
Class 4 can involve short steep sections where the use of a rope is recommended, and un-roped falls could be fatal.
Class 5 is considered true rock climbing, predominantly on vertical or near vertical rock, and requires skill and a rope to proceed safely. Un-roped falls would result in severe injury or death
