video tutorial drawing isolines - Free Printable

To solve this task, we need to draw the 30-inch isoline on the map showing December snowfall amounts. An isoline (or contour line) connects points of equal value—in this case, areas with 30 inches of snowfall.

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🔍 Step-by-Step Guide:

#### 1. Understand What an Isoline Is
An isoline connects locations with the same value. Here, the 30" isoline will connect all points where the snowfall is exactly 30 inches.

#### 2. Locate All Data Points Near 30 Inches
Scan the map and identify all values close to 30 inches:
- 34.0 (near western New York)
- 31.0 (two locations: one near central NY, one in PA)
- 30.5 (one location)
- 30.0 (one location — likely a key point)
- 29.0, 28.0, etc., are below 30
- 32.0, 33.2, 39.0 are above

We’re looking for places where the snowfall is exactly 30 inches, or between 29–31 inches so that we can interpolate the 30" line.

But since we're drawing a 30" isoline, we want to draw a smooth line that passes through or between values such that it represents 30 inches.

#### 3. Find Where 30 Inches Occurs
Look at these key spots:
- 30.0 – directly labeled
- 30.5 – slightly above
- 31.0 – above
- 29.0 – below
- 28.0, 26.0, etc. – too low

So, the 30" isoline should go through or near:
- The 30.0 spot
- Between 29.0 and 31.0 values
- Between 28.0 and 32.0, etc.

#### 4. Interpolate Between Values
If two adjacent points have values on either side of 30, the 30" isoline must pass between them, closer to the lower value if the difference is large.

For example:
- Between 28.0 and 32.0: 30 is halfway → draw line midway
- Between 29.0 and 31.0: 30 is halfway → again, midpoint
- Between 30.5 and 28.0: 30 is closer to 30.5 → line closer to 30.5

#### 5. Trace the 30" Isoline
Now, let's trace the path based on data:

Start from the western edge of New York:
- There’s a 34.0 (very high), then 31.0, 30.5, 30.0
- So, the 30" line goes through or just south of 30.0, and between 30.5 and 29.0
- Then move southeast toward Pennsylvania

In Pennsylvania:
- A 31.0 is marked near the border
- Nearby is 28.0, 29.0, 24.0
- So, the 30" line should pass between 29.0 and 31.0, possibly curving around the higher values

Then, further east:
- 31.0 in NJ (northern part), but 17.0, 13.2, 11.0 nearby — too low
- So, the 30" line ends somewhere in northern NJ/Pennsylvania border area

#### 6. Final Shape of the 30" Isoline
The 30" isoline should:
- Start in western New York, near the 30.0 and 30.5 values
- Curve southwest into Pennsylvania, passing near 31.0 and 29.0
- Possibly loop around the 32.0 and 33.2 values (which are higher than 30)
- End in northern New Jersey, near the 31.0 and 17.0 transition

It will be a closed or semi-closed loop around the highest snowfall areas.

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✔ How to Draw It:

Use a smooth curve that:
- Passes through the 30.0 point
- Lies between 29.0 and 31.0 where they are adjacent
- Avoids going through values below 29 or above 31 unless interpolating properly
- Follows the general pattern of increasing snowfall toward the west/northwest

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📌 Final Answer:

> Draw a smooth line connecting all points where snowfall equals 30 inches. This line should pass through or between values like 30.0, 30.5, and 31.0, and lie between 29.0 and 31.0 where appropriate. It will form a curved boundary enclosing the highest snowfall areas in western New York and northern Pennsylvania.

You would draw this by hand on the map using a pencil or digital tool, making sure the line is continuous and smooth.

Let me know if you'd like a sketch description or coordinates!